RESUMO
Lichens are symbiotic organisms that are well adapted to desiccation/rehydration cycles. Over the last decades, the physiological background of their photosynthetic response-specifically activation of the protective mechanism during desiccation-has been studied at the level of photosystem II of the lichen photobiont by means of several biophysical methods. In our study, the effects of desiccation and low temperatures on chlorophyll fluorescence and spectral reflectance parameters were investigated in Antarctic chlorolichen Dermatocarpon polyphyllizum. Lichen thalli were collected from James Ross Island, Antarctica, and following transfer to a laboratory, samples were fully hydrated and exposed to desiccation at temperatures of 18, 10, and 4 °C. During the desiccation process, the relative water content (RWC) was measured gravimetrically and photosynthetic parameters related to the fast transient of chlorophyll fluorescence (OJIP) were measured repeatedly. Similarly, the change in spectral reflectance parameters (e.g., NDVI, PRI, G, NPCI) was monitored during thallus dehydration. The dehydration-response curves showed a decrease in a majority of the OJIP-derived parameters (e.g., maximum quantum yield of photosystem II photochemistry: FV/FM, and performance index: PI in D. polyphyllizum, which were more apparent at RWCs below 20%. The activation of protective mechanisms in severely dehydrated thalli was documented by increased thermal dissipation (DI0/RC) and its quantum yield (Phi_D0). Low temperature accelerated these processes. An analysis of the OJIP shape reveals the presence of K-bands (300 µs), and L-bands (80 µs), which can be attributed to dehydration-induced stress. Spectral reflectance indices decreased in a majority of cases with an RWC decrease and were positively related to the OJIP-derived parameters: FV/FM (capacity of photosynthetic processes in PSII), Phi_E0 (effectiveness of electron transport), and PI_tot (total performance index), which was more apparent in NDVI. A negative relation was found for NPCI. These indices could be used in follow-up ecophysiological photosynthetic studies of lichens that are undergoing rehydration/dehydration cycles.
Assuntos
Adaptação Fisiológica , Ascomicetos/fisiologia , Líquens/fisiologia , Fotossíntese , Complexo de Proteína do Fotossistema II/metabolismo , Regiões Antárticas , Temperatura Baixa , Desidratação , Dessecação , Água/fisiologiaRESUMO
The soil microalgae of the genus Heterococcus are found in cold environments and have been reported for the terrestrial ecosystems of several Sub-Antarctic and Antarctic Islands. This study focused on resistance of Heterococcus sp. to sub-zero temperature. Heterococcus sp. was isolated from soil samples from James Ross Island, Antarctica. Culture of Heterococcus sp. grown in liquid medium were used to study ribitol effects at sub-zero temperatures on the species resistance to rapid freezing (RF, immersion of a sample into liquid nitrogen) and consequent cultivation on agar. Before the experiment, Heterococcus sp. was cultured in liquid medium for 11 months and then treated in ribitol concentrations of 32 or 50â¯mM for 2â¯h. Then, 1â¯ml samples were frozen to -196⯰C in liquid nitrogen (day 0) and inoculated on BBM agar after thawing. Number of living and dead cells was evaluated and the cell viability (Pν) was calculated repeatedly using the optical microscopy approach. The addition of ribitol caused a noticable increase in Pν on days 9, 12, 14 (with a Pν of 25-45% in ribitol-treated samples compared to 10% in the untreated control). In the following period (d 16-19), the positive effect of ribitol on Pν was less pronounced but still statistically significant. To evaluate the negative effects of RF on chlorophyll fluorescence parameters, the potential yield of photochemical reactions in PS II (FV/FM), and the effective quantum yield of photochemical reactions in PS II (ФPSII) were measured immediately before and after RF. Consequently, FV/FM and ФPSII of agar inoculates were measured repeatedly for 30â¯d cultivation in 3â¯d interval. Both the 32 and the 50â¯mM addition of ribitol caused earlier detection of the parameters (d 16) compared to the control measurements (d 23) as well as reaching the maximum values of the chlorophyll fluorescence parameters earlier (d 23 in ribitol-treated samples compared to d 25 in control samples). Heterococcus sp. proved to be a species resistant to rapid freezing. The ability may help the species to survive in harsh Antarctic environments typified by rapid fluctuations in temperature that may bring a rapid freezing of the alga.
Assuntos
Adaptação Fisiológica/fisiologia , Sobrevivência Celular/fisiologia , Clorofila/metabolismo , Microalgas/fisiologia , Regiões Antárticas , Sobrevivência Celular/efeitos dos fármacos , Temperatura Baixa , Fluorescência , Congelamento , Ribitol/metabolismo , Ribitol/farmacologiaRESUMO
Four rod-shaped and Gram-stain-negative bacterial strains, CCM 8647, CCM 8649T, CCM 8643T and CCM 8648T, were isolated from rock samples collected on James Ross Island, Antarctica. Extensive biotyping, fatty acid profiling, chemotaxonomy, 16S rRNA gene sequencing and whole-genome sequencing was applied to isolates to clarify their taxonomic position. Phylogenetic analysis based on 16S rRNA gene sequencing indicated that all four isolates belonged to the genus Hymenobacter. Strains CCM 8649T and CCM 8647 were most closely related to Hymenobacter arizonensis OR362-8T (94.4â% 16S rRNA gene sequence similarity), strain CCM 8643T to Hymenobacter terrae DG7AT (96.3â%) and strain CCM 8648T to Hymenobacter glaciei VUG-A130T (96.3â%). The predominant fatty acids of CCM 8649T and CCM 8647 were summed feature 3 (C16â:â1ω7c/C16â:â1ω6c), C16â:â1ω5c and iso-C15â:â0, whereas those of CCM 8643T and CCM 8648T were summed feature 3 (C16â:â1ω7c/C16â:â1ω6c) and C16â:â1ω5c. The quinone systems contained exclusively menaquinone MK-7. The major polyamine was sym-homospermidine. All four strains contained the major polar lipid phosphatidylethanolamine. The G+C content of genomic DNA ranged from 60-63 mol%. Whole-genome sequencing data supported the finding that isolates represented distinct species of the genus Hymenobacter. On the basis of the results obtained, three novel species are proposed for which the names Hymenobacter coccineus sp. nov., Hymenobacter lapidarius sp. nov. and Hymenobacter glacialis sp. nov. are suggested, with the type strains CCM 8649T (=LMG 29441T=P5239T), CCM 8643T (=LMG 29435T=P3150T) and CCM 8648T (=LMG 29440T=P5086T), respectively.
Assuntos
Filogenia , Regiões Antárticas , Técnicas de Tipagem Bacteriana , Composição de Bases , Cytophagaceae/classificação , DNA Bacteriano/genética , Ácidos Graxos/química , Fosfatidiletanolaminas/química , Pigmentação , RNA Ribossômico 16S/genética , Análise de Sequência de DNA , Espermidina/análogos & derivados , Espermidina/química , Vitamina K 2/análogos & derivados , Vitamina K 2/químicaRESUMO
A bacterial strain designated CCM 8645T was isolated from a soil sample collected nearby a mummified seal carcass in the northern part of James Ross Island, Antarctica. The cells were short rods, Gram-stain-negative, non-motile, catalase and oxidase positive, and produced a red-pink pigment on R2A agar. A polyphasic taxonomic approach based on 16S rRNA gene sequencing, extensive biotyping using conventional tests and commercial identification kits and chemotaxonomic analyses were applied to clarify its taxonomic position. Phylogenetic analysis based on the 16S rRNA gene placed strain CCM 8645T in the genus Mucilaginibacter with the closest relative being Mucilaginibacter daejeonensis Jip 10T, exhibiting 96.5â% 16S rRNA pairwise similarity which was clearly below the 97â% threshold value recommended for species demarcation. The major components in fatty acid profiles were Summed feature 3 (C16â:â1ω7c/C16â:â1ω6c), C15â:â0 iso and C17â:â0 iso 3OH. The cellular quinone content was exclusively menaquinone MK-7. The major polyamine was sym-homospermidine and predominant polar lipids were phosphatidylethanolamine and phosphatidylserine. Based on presented results, we propose a novel species for which the name Mucilaginibacter terrae sp. nov. is suggested, with the type strain CCM 8645T (=LMG 29437T).
Assuntos
Bacteroidetes/classificação , Filogenia , Microbiologia do Solo , Regiões Antárticas , Técnicas de Tipagem Bacteriana , Bacteroidetes/genética , Bacteroidetes/isolamento & purificação , Composição de Bases , DNA Bacteriano/genética , Ácidos Graxos/química , Fosfatidiletanolaminas/química , Fosfatidilserinas/química , Pigmentação , RNA Ribossômico 16S/genética , Análise de Sequência de DNA , Espermidina/análogos & derivados , Espermidina/química , Vitamina K 2/análogos & derivados , Vitamina K 2/químicaRESUMO
Strain P4487AT was isolated during investigation of cultivable bacterial populations of environmental materials sampled at James Ross Island, Antarctica. It revealed Gram-stain-negative short rod-shaped cells producing a pink pigment. Phylogenetic analysis based on 16S rRNA gene sequences allocated strain P4487AT to the genus Pedobacter but showed that the strain represents a distinct intrageneric phylogenetic lineage clearly separated from remaining Pedobacter species. Phylogenetically, strain P4487AT formed a common branch with the Pedobacter arcticus and Pedobacter lignilitoris cluster while the highest value of 94.4â% 16S rRNA gene sequence similarity suggested that Pedobacter lentus is the most closely related species. Biochemical and physiological test results enabled the differentiation of strain P4487AT from all phylogenetically closely related species. Chemotaxonomic analyses of strain P4487AT showed MK-7 as the respiratory menaquinone, sym-homospermidine as the major polyamine, phosphatidylethanolamine and two unidentified lipids as the major polar lipids, presence of sphingolipids, and C16â:â1ω7c/C16â:â1ω6c (summed feature 3), iso-C15â:â0 and iso-C17â:â0 3-OH as the major fatty acids, all of which corresponded with characteristics of the genus Pedobacter. The results showed that strain P4487AT represents a novel species within the genus Pedobacter, for which the name Pedobacter psychrophilus sp. nov. is proposed. The type strain is P4487AT (=CCM 8644T=LMG 29436T).
Assuntos
Pedobacter/classificação , Filogenia , Microbiologia do Solo , Regiões Antárticas , Técnicas de Tipagem Bacteriana , Composição de Bases , DNA Bacteriano/genética , Ácidos Graxos/química , Pedobacter/genética , Pedobacter/isolamento & purificação , Fosfatidiletanolaminas/química , Pigmentação , RNA Ribossômico 16S/genética , Análise de Sequência de DNA , Espermidina/análogos & derivados , Espermidina/química , Esfingolipídeos/química , Vitamina K 2/análogos & derivados , Vitamina K 2/químicaRESUMO
A taxonomic study performed on 17 Gram-stain-negative rod-shaped bacterial strains originating from the Antarctic environment is described. Initial phylogenetic analysis using 16S rRNA gene sequencing differentiated the strains into four groups belonging to the genus Pedobacter but they were separated from all hitherto described Pedobacter species. Group I (n=8) was closest to Pedobacter aquatilis (97.8â% 16S rRNA gene sequence similarity). Group II (n=2) and group III (n=4) were closely related (98.8â% 16S rRNA gene sequence similarity) and had Pedobacter jejuensis as their common nearest neighbour. Group IV (n=3) was distantly delineated from the remaining Pedobacter species. Differentiation of the analysed strains into four clusters was further confirmed by repetitive sequence-based PCR fingerprinting, ribotyping, DNA-DNA hybridization and phenotypic traits. Common to representative strains for the four groups were the presence of major menaquinone MK-7, sym-homospermidine as the major polyamine, phosphatidylethanolamine, two unidentified lipids (L2, L5) and an unidentified aminolipid (AL2) as the major polar lipids, presence of an alkali-stable lipid, and C16:1ω7c/C16:1ω6c (summed feature 3), iso-C15:0 and iso-C 17:0 3-OH as the major fatty acids, which corresponded to characteristics of the genus Pedobacter. The obtained results showed that the strains analysed represent four novel species of the genus Pedobacter, for which the names Pedobacter jamesrossensis sp. nov. (type strain CCM 8689T=LMG 29684T), Pedobacter lithocola sp. nov. (CCM 8691T=LMG 29685T), Pedobacter mendelii sp. nov. (CCM 8685T=LMG 29688T) and Pedobacter petrophilus sp. nov. (CCM 8687T=LMG 29686T) are proposed.
Assuntos
Pedobacter/classificação , Filogenia , Regiões Antárticas , Técnicas de Tipagem Bacteriana , Composição de Bases , DNA Bacteriano/genética , Ácidos Graxos/química , Hibridização de Ácido Nucleico , Pedobacter/genética , Pedobacter/isolamento & purificação , Fosfatidiletanolaminas/química , RNA Ribossômico 16S/genética , Análise de Sequência de DNA , Espermidina/análogos & derivados , Espermidina/química , Vitamina K 2/análogos & derivados , Vitamina K 2/químicaRESUMO
Lichens are efficient and cost-effective biomonitors of the environment. Their geographic distribution together with their slow growth rate enable investigation of the deposition patterns of various elements and substances. In this research, levels of cadmium, lead, and mercury in Usnea antarctica lichens in the area of James Ross Island, Antarctica, were investigated. The lichens were microwave-digested, and the metals were determined by means of atomic absorption spectrometry with graphite furnace and a direct mercury analyzer. Median total contents of Cd, Hg, and Pb were 0.04, 0.47, and 1.6 mg/kg in whole lichens, respectively. The bottom-up distributions of these metals in the fruticose lichen thalli were investigated, and it was revealed that the accumulation patterns for mercury and lead were opposite to that for cadmium. The probable reason for this phenomenon may lie in the inner structure of thalli. The total contents of metals were comparable with those published for other unpolluted areas of maritime Antarctica. However, this finding was not expected for mercury, since the sampling locality was close to an area with some of the highest mercury contents published for Antarctic lichens. In short, lichens proved their usability as biological monitors, even in harsh conditions. However, the findings emphasize the need to take into account the distributions of elements both in the environment and in the lichen itself.
Assuntos
Poluentes Atmosféricos/análise , Monitoramento Ambiental/métodos , Metais/análise , Usnea/química , Regiões Antárticas , Ascomicetos , Cádmio/análise , Ilhas , Chumbo/análise , Líquens/química , Mercúrio/análise , Quinolonas , Espectrofotometria AtômicaRESUMO
Extremophilic lichens and their photosynthesizing photobionts from the cold regions of Earth are adapted to perform photosynthesis at subzero temperatures. To evaluate interspecific differences in the critical temperature for primary photochemical processes of photosynthesis, we exposed lichen thalli of Usnea antarctica, Usnea aurantiaco-atra, and Umbilicaria cylindrica to linear cooling from +20 to -50 °C at a constant rate of 2 °C min-1. Simultaneously, two chlorophyll fluorescence parameters (FV/FM - potential yield of photosynthetic processes in photosystem II, ΦPSII - effective quantum yield of PS II) evaluating a gradual subzero temperature-induced decline in photosynthetic processes were measured by a modulated fluorometer. For the studied species, the response of FV/FM and ΦPSII to declining temperature showed an S-curve shape. The decline in FV/FM and ΦPSII at low temperatures started at -5 and +5 °C, respectively in the majority of cases. The decline was, however, species-specific. U. aurantiaco-atra showed a constant-rate decline of ΦPSII from the physiological temperature 20 °C. U. antarctica exhibited the first sign of FV/FM decline at -12 °C. The critical temperature related to full inhibition of the photosynthetic processes in PSII (FV/FM), was found at -20 °C. However, this occurred at -30 °C for U. cylindrica. In an individual sample, the critical temperature for FV/FM was typically lower than for ΦPSII. The method of linear cooling combined with simultaneous measurements of chlorophyll fluorescence parameters proved to be an efficient tool in the estimation of extremophilic species sensitivity/resistance to freezing.
Assuntos
Adaptação Fisiológica/fisiologia , Extremófilos/fisiologia , Líquens/fisiologia , Fotossíntese/fisiologia , Clorofila/análise , Temperatura Baixa , Congelamento , Complexo de Proteína do Fotossistema II/fisiologia , Especificidade da EspécieRESUMO
During the microbiological research performed within the scope of activities of Czech expeditions based at the Johann Gregor Mendel Station at James Ross Island, Antarctica, two psychrotrophic gram-stain negative non-fluorescent strains CCM 8506T and CCM 8507 from soil were extensively characterized using genotypic and phenotypic methods. Initial characterization using ribotyping with HindIII restriction endonuclease and phenotyping implies that both isolates belong to a single Pseudomonas species. Sequencing of rrs, rpoB, rpoD and glnA genes of strain CCM 8506(T) confirmed affiliation of investigated strains within the genus Pseudomonas. Further investigation using automated ribotyping with EcoRI (RiboPrinter(®) Microbial Characterisation System), whole-cell protein profiling using the Agilent 2100 Bioanalyzer system, extensive biochemical testing and DNA-DNA hybridization experiments confirmed that both investigated strains are members of a single taxon which is clearly separated from all hitherto described Pseudomonas spp. Based on all findings, we describe a novel species Pseudomonas gregormendelii sp. nov. with the type strain CCM 8506(T) (=LMG 28632T).
Assuntos
Pseudomonas/isolamento & purificação , Microbiologia do Solo , Regiões Antárticas , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , DNA Bacteriano/genética , DNA Ribossômico/genética , Filogenia , Pseudomonas/classificação , Pseudomonas/genética , Pseudomonas/metabolismo , RNA Ribossômico 16S/genéticaRESUMO
This study explores and compares the limits for photosynthesis in subzero temperatures of six Antarctic lichens: Sphaerophorus globosus, Caloplaca regalis, Umbilicaria antarctica, Pseudephebe minuscula, Parmelia saxatilis and Lecania brialmontii combining linear cooling and chlorophyll fluorescence methods. The results revealed triphasic S-curves in the temperature response of the maximum quantum yield (FV/FM) and effective quantum yield of photosystem II (ΦPSII) for all species. All investigated species showed a high level of cryoresistance with critical temperatures (Tc) below -20 °C. However, record low Tc temperatures have been discovered for L. brialmotii (-54 °C for FV/FM and -40 °C for ΦPSII) and C. regalis (-52 °C for FV/FM and -38 °C for ΦPSII). Additionally, the yield differentials (FV/FM - ΦPSII) in functions of temperature revealed one or two peaks, with the larger one occurring for temperatures below -20 °C for the above-mentioned species. Finally, Kautsky kinetics were measured and compared at different temperatures (20 °C, 10 °C, 0 °C and -10 °C and then -10 °C after 1 h of incubation). This research serves as a foundation for further developing investigations into the biophysical mechanisms by which photosynthesis is carried out at subzero temperatures.
Assuntos
Clorofila , Líquens , Congelamento , Temperatura , Líquens/fisiologia , Complexo de Proteína do Fotossistema II , Fluorescência , FotossínteseRESUMO
Antarctica provides a unique environment for studying human adaptability, characterized by controlled conditions, limited sensory stimulation, and significant challenges in logistics and communication. This longitudinal study investigates the relationship between stress indicators, with a specific focus on mean sleep heart rate, during a COVID-19 quarantine and subsequent 83 days long summer Antarctic expedition at the J. G. Mendel Czech Antarctic Station. Our novel approach includes daily recordings of sleep heart rate and weekly assessments of emotions, stress, and sleep quality. Associations between variables were analyzed using the generalized least squares method, providing unique insights into nuances of adaptation. The results support previous findings by providing empirical evidence on the stress reducing effect of Antarctic summer expedition and highlight the importance of previous experience and positive emotions, with the novel contribution of utilizing physiological data in addition to psychological measures. High-frequency sampling and combination of psychological and physiological data addresses a crucial gap in the research of stress. This study contributes valuable knowledge to the field of psychophysiology and has implications for expedition planners, research organizations, teams in action settings, pandemic prevention protocols, global crises, and long-duration spaceflight missions. Comprehensive insights promote the well-being and success of individuals in extreme conditions.
Assuntos
Expedições , Humanos , Regiões Antárticas , Estudos Longitudinais , Sono , PsicofisiologiaRESUMO
During Czech expeditions at James Ross Island, Antarctica, in the years 2007-2009, the bacterial diversity of the genus Pseudomonas was studied. Twelve fluorescent Pseudomonas strains were isolated from various samples and were subjected to a detailed taxonomic study. A polyphasic approach included genotypic and phenotypic analyses. The genotypic analysis involved sequencing of rrs, rpoB and rpoD genes, DNA-DNA hybridization (DDH) studies as well as manual ribotyping using HindIII endonuclease. The phenotypic characterization included conventional tests as well as biotyping using the Biolog system, protein profiling by SDS-PAGE, and MALDI-TOF MS analysis. Our taxonomic study revealed that all isolates belonged to the same Pseudomonas species with psychrotrophic growth not exceeding 37 °C. The cultures showed a unique position among the phylogenetically related pseudomonads. DDH experiment between the proposed type strain of the antarctic isolates and the closest neighbour P. arsenicoxydans CCM 8423(T) showed only 40.9-50.1 % similarity, thus confirming that the characterized strains do not belong to the P. arsenicoxydans species. According to the results obtained we propose the name P. prosekii sp. nov. for this novel Pseudomonas taxon with type strain AN/28/1(T) (=CCM 7990(T) and LMG 26867(T)).
Assuntos
Microbiologia Ambiental , Pseudomonas/classificação , Pseudomonas/isolamento & purificação , Regiões Antárticas , Técnicas de Tipagem Bacteriana , Análise por Conglomerados , DNA Bacteriano/química , DNA Bacteriano/genética , DNA Ribossômico/química , DNA Ribossômico/genética , RNA Polimerases Dirigidas por DNA/genética , Dados de Sequência Molecular , Hibridização de Ácido Nucleico , Filogenia , Pseudomonas/genética , Pseudomonas/fisiologia , RNA Ribossômico 16S/genética , Ribotipagem , Análise de Sequência de DNA , Fator sigma/genéticaRESUMO
Hydroponic experiments were performed to examine the effect of prolonged sulfate limitation combined with cadmium (Cd) exposure in Arabidopsis thaliana and a potential Cd hyperaccumulator, Nicotiana tabacum. Low sulfate treatments (20 and 40 µM MgSO4) and Cd stress (4 µM CdCl2) showed adverse effects on morphology, photosynthetic and biochemical parameters and the nutritional status of both species. For example, Cd stress decreased NO3- root content under 20 µM MgSO4 to approximately 50% compared with respective controls. Interestingly, changes in many measured parameters, such as chlorophyll and carotenoid contents, the concentrations of anions, nutrients and Cd, induced by low sulfate supply, Cd exposure or a combination of both factors, were species-specific. Our data showed opposing effects of Cd exposure on Ca, Fe, Mn, Cu and Zn levels in roots of the studied plants. In A. thaliana, levels of glutathione, phytochelatins and glucosinolates demonstrated their distinct involvement in response to sub-optimal growth conditions and Cd stress. In shoot, the levels of phytochelatins and glucosinolates in the organic sulfur fraction were not dependent on sulfate supply under Cd stress. Altogether, our data showed both common and species-specific features of the complex plant response to prolonged sulfate deprivation and/or Cd exposure.
Assuntos
Arabidopsis , Fitoquelatinas , Cádmio/toxicidade , Nicotiana , Sulfatos/farmacologia , Glucosinolatos/farmacologia , Nutrientes , Suplementos Nutricionais , Raízes de PlantasRESUMO
The Antarctic lichen, Xanthoria elegans, in its hydrated state has several physiological mechanisms to cope with high light effects on the photosynthetic processes of its photobionts. We aim to investigate the changes in primary photochemical processes of photosystem II in response to a short-term photoinhibitory treatment. Several chlorophyll a fluorescence techniques: (1) slow Kautsky kinetics supplemented with quenching mechanism analysis; (2) light response curves of photosynthetic electron transport (ETR); and (3) response curves of non-photochemical quenching (NPQ) were used in order to evaluate the phenomenon of photoinhibition of photosynthesis and its consequent recovery. Our findings suggest that X. elegans copes well with short-term high light (HL) stress due to effective photoprotective mechanisms that are activated during the photoinhibitory treatment. The investigations of quenching mechanisms revealed that photoinhibitory quenching (qIt) was a major non-photochemical quenching in HL-treated X. elegans; qIt relaxed rapidly and returned to pre-photoinhibition levels after a 120 min recovery. We conclude that the Antarctic lichen species X. elegans exhibits a high degree of photoinhibition resistance and effective non-photochemical quenching mechanisms. This photoprotective mechanism may help it survive even repeated periods of high light during the early austral summer season, when lichens are moist and physiologically active.
RESUMO
A polyphasic taxonomic approach was used to characterize the four strains P2653T, P2652, P2498, and P2647, isolated from Antarctic regolith samples. Initial genotype screening performed by PCR fingerprinting based on repetitive sequences showed that the isolates studied formed a coherent cluster separated from the other Pseudomonas species. Identification results based on 16S rRNA gene sequences showed the highest sequence similarity with Pseudomonas graminis (99.7%), which was confirmed by multilocus sequence analysis using the rpoB, rpoD, and gyrB genes. Genome sequence comparison of P2653T with the most related P. graminis type strain DSM 11363T revealed an average nucleotide identity of 92.1% and a digital DNA-DNA hybridization value of 46.6%. The major fatty acids for all Antarctic strains were C16:0, Summed Feature 3 (C16:1ω7c/C16:1ω6c) and Summed Feature 8 (C18:1ω7c/C18:1ω6c). The predominant respiratory quinone was Q-9, and the major polar lipids were phosphatidylethanolamine, diphosphatidylglycerol, and phosphatidylglycerol. The regolith strains could be differentiated from related species by the absence of arginine dihydrolase, ornithine and lysine decarboxylase and by negative tyrosine hydrolysis. The results of this polyphasic study allowed the genotypic and phenotypic differentiation of four analysed strains from the closest related species, which confirmed that the strains represent a novel species within the genus Pseudomonas, for which the name Pseudomonas petrae sp. nov. is proposed with P2653T (CCM 8850T = DSM 112068T = LMG 30619T) as the type strain.
Assuntos
Genes Bacterianos , Fosfolipídeos , Fosfolipídeos/análise , Regiões Antárticas , Análise de Sequência de DNA , RNA Ribossômico 16S/genética , Filogenia , Ácidos Graxos/análise , Pseudomonas , DNA , DNA Bacteriano/genética , Técnicas de Tipagem BacterianaRESUMO
Climate warming in the Antarctic tundra will affect locally dominant cryptogams. Being adapted to low temperatures and freezing, little is known about the response of the polar lichens' primary photochemistry to warming and desiccation. Since 2008, we have monitored the ecophysiological responses of lichens to the future warming scenario during a long-term warming experiment through open top chambers (OTCs) on Fildes Peninsula. We studied the primary photochemical response (potential Fv/Fm and effective efficiency of photosystem II YPSII) of different lichen taxa and morphotypes under desiccation kinetics and heat shock experiments. As lichens grow slowly, to observe changes during warming we methodologically focused on carbon and nitrogen content as well as on the stable isotope ratios. Endemic Himantormia lugubris showed the strongest effect of long-term warming on primary photochemistry, where PSII activity occurred at a lower %RWC inside the OTCs, in addition to higher Fv/Fm values at 30 °C in the heat shock kinetic treatment. In contrast, Usnea aurantiaco-atra did not show any effect of long-term warming but was active at a thallus RWC lower than 10%. Both Cladonia species were most affected by water stress, with Cladonia aff. gracilis showing no significant differences in primary photochemical responses between the warming and the control but a high sensibility to water deficiency, where, at 60% thallus RWC, the photochemical parameters began to decrease. We detected species-specific responses not only to long-term warming, but also to desiccation. On the other hand, the carbon content did not vary significantly among the species or because of the passive warming treatment. Similarly, the nitrogen content showed non-significant variation; however, the C/N ratio was affected, with the strongest C/N decrease in Cladonia borealis. Our results suggest that Antarctic lichens can tolerate warming and high temperature better than desiccation and that climate change may affect these species if it is associated with a decrease in water availability.
RESUMO
Five macrolichens of different thallus morphology from Antarctica (King George Island) were used for this ecophysiological study. The effect of thallus desiccation on primary photosynthetic processes was examined. We investigated the lichens' responses to the relative water content (RWC) in their thalli during the transition from a wet (RWC of 100%) to a dry state (RWC of 0%). The slow Kautsky kinetics of chlorophyll fluorescence (ChlF) that was recorded during controlled dehydration (RWC decreased from 100 to 0%) and supplemented with a quenching analysis revealed a polyphasic species-specific response of variable fluorescence. The changes in ChlF at a steady state (Fs), potential and effective quantum yields of photosystem II (FV/FM, ΦPSII), and nonphotochemical quenching (NPQ) reflected a desiccation-induced inhibition of the photosynthetic processes. The dehydration-dependent fall in FV/FM and ΦPSII was species-specific, starting at an RWC range of 22-32%. The critical RWC for ΦPSII was below 5%. The changes indicated the involvement of protective mechanisms in the chloroplastic apparatus of lichen photobionts at RWCs of below 20%. In both the wet and dry states, the spectral reflectance curves (SRC) (wavelength 400-800 nm) and indices (NDVI, PRI) of the studied lichen species were measured. Black Himantormia lugubris showed no difference in the SRCs between wet and dry state. Other lichens showed a higher reflectance in the dry state compared to the wet state. The lichen morphology and anatomy data, together with the ChlF and spectral reflectance data, are discussed in relation to its potential for ecophysiological studies in Antarctic lichens.
RESUMO
Lichens survive harsh weather of Antarctica as well as of other hostile environments worldwide. Therefore, this investigation is important to understand the evolution of life on Earth in relation to their stress tolerance strategy. We have used chlorophyll a fluorescence (ChlF) and Raman spectroscopy, respectively, to monitor the activation/deactivation of photosynthesis and carotenoids in three diverse Antarctic lichens, Dermatocarpon polyphyllizum (DP), Umbilicaria antarctica (UA), and Leptogium puberulum (LP). These lichens, post 4 h or 24 h of hydration, showed differences in their ChlF transients and values of major ChlF parameters, e.g., in the maximum quantum efficiency of PSII photochemistry (Fv/Fm), and yields of fluorescence and heat dissipation (Φf,d), of effective quantum efficiency of PSII photochemistry (ΦPSII) and of non-photochemical quenching (Φnpq), which may be due to quantitative and/or qualitative differences in the composition of their photobionts. For understanding the kinetics of hydration-induced activation of photosynthesis, we screened ΦPSII of these lichens and reported its non-linear stimulation on a minute time scale; half of the activation time (t1/2) was fastest ~4.05 ± 0.29 min for DP, which was followed by 5.46 ± 0.18 min for UA, and 13.95 ± 1.24 min for LP. Upon drying of fully activated lichen thallus, there was a slow decay, in hours, of relative water content (RWC) as well as of Fv/Fm. Raman spectral signatures were different for lichens having algal (in DP and UA) and cyanobacteria (in LP) photobionts, and there was a significant shift in ν1(C=C) Raman band of carotenoids post 24 h hydration as compared to their value at a dry state or post 4 h of hydration; this shift was decreased, when drying, in DP and LP but not in UA. We conclude that hydration nonlinearly activated photosynthetic apparatus/reactions of these lichens in minute time range but there was a de-novo synthesis of chlorophylls as well as of carotenoids post 24 h. Their dehydration-induced deactivation, however, was comparatively slow, in hours range, and there seemed a degradation of synthesized chlorophylls and carotenoids post dryness. We conclude that in extremophilic lichens, their photosynthetic partners, in particular, possess a complex survival and photoprotective strategy to be successful in the extreme terrestrial environments in Antarctica.
Assuntos
Líquens , Regiões Antárticas , Ascomicetos , Carotenoides/metabolismo , Clorofila , Clorofila A , Fluorescência , Líquens/metabolismo , Fotossíntese , Análise Espectral RamanRESUMO
High temperatures represent a limitation for growth and development of many crop species. Several studies have demonstrated that the yield reduction of tomato under high temperatures and drought is mainly due to a photosynthetic decline. In this paper, a set of 15 tomato genotypes were screened for tolerance to elevated temperatures by cultivating plants under plastic walk-in tunnels. To assess the potential tolerance of tomato genotypes to high temperatures, measurements of chlorophyll fluorescence, pigments content and leaf functional traits have been carried out together with the evaluation of the final yields. Based on the greenhouse trials, a group of eight putative heat-sensitive and heat-tolerant tomato genotypes was selected for laboratory experiments aimed at investigating the effects of short-term high temperatures treatments in controlled conditions. The chlorophyll fluorescence induction kinetics were recorded on detached leaves treated for 60 min at 35 °C or at 45 °C. The last treatment significantly affected the photosystem II (PSII) photochemical efficiency (namely maximum PSII quantum efficiency, Fv/Fm, and quantum yield of PSII electron transport, ΦPSII) and the non-photochemical quenching (NPQ) in the majority of genotypes. The short-term heat shock treatments also led to significant differences in the shape of the slow Kautsky kinetics and its significant time points (chlorophyll fluorescence levels minimum O, peak P, semi-steady state S, maximum M, terminal steady state T) compared to the control, demonstrating heat shock-induced changes in PSII functionality. Genotypes potentially tolerant to high temperatures have been identified. Our findings support the idea that chlorophyll fluorescence parameters (i.e., ΦPSII or NPQ) and some leaf functional traits may be used as a tool to detect high temperatures-tolerant tomato cultivars.
RESUMO
Bacteria of the genus Massilia often colonize extreme ecosystems, however, a detailed study of the massilias from the Antarctic environment has not yet been performed. Here, sixty-four Gram-stain-negative, aerobic, motile rods isolated from different environmental samples on James Ross Island (Antarctica) were subjected to a polyphasic taxonomic study. The psychrophilic isolates exhibited slowly growing, moderately slimy colonies revealing bold pink-red pigmentation on R2A agar. The set of strains exhibited the highest 16S rRNA gene sequence similarities (99.5-99.9%) to Massilia violaceinigra B2T and Massilia atriviolacea SODT and formed several phylogenetic groups based on the analysis of gyrB and lepA genes. Phenotypic characteristics allowed four of them to be distinguished from each other and from their closest relatives. Compared to the nearest phylogenetic neighbours the set of six genome-sequenced representatives exhibited considerable phylogenetic distance at the whole-genome level. Bioinformatic analysis of the genomic sequences revealed a high number of putative genes involved in oxidative stress response, heavy-metal resistance, bacteriocin production, the presence of putative genes involved in nitrogen metabolism and auxin biosynthesis. The identification of putative genes encoding aromatic dioxygenases suggests the biotechnology potential of the strains. Based on these results four novel species and one genomospecies of the genus Massilia are described and named Massilia rubra sp. nov. (P3094T=CCM 8692T=LMG 31213T), Massilia aquatica sp. nov. (P3165T=CCM 8693T=LMG 31211T), Massilia mucilaginosa sp. nov. (P5902T=CCM 8733T=LMG 31210T), and Massilia frigida sp. nov. (P5534T=CCM 8695T=LMG 31212T).