Soil microbiome analysis reveals effects of periodic waterlogging stress on sugarcane growth.

Sugarcane is one of the major agricultural crops with high economic importance in Thailand. Periodic waterlogging has a long-term negative effect on sugarcane development, soil properties, and microbial diversity, impacting overall sugarcane production. Yet, the microbial structure in periodically waterlogged sugarcane fields across soil compartments and growth stages in Thailand has not been documented. This study investigated soil and rhizosphere microbial communities in a periodic waterlogged field in comparison with a normal field in a sugarcane plantation in Ratchaburi, Thailand, using 16S rRNA and ITS amplicon sequencing. Alpha diversity analysis revealed comparable values in periodic waterlogged and normal fields across all growth stages, while beta diversity analysis highlighted distinct microbial community profiles in both fields throughout the growth stages. In the periodic waterlogged field, the relative abundance of Chloroflexi, Actinobacteria, and Basidiomycota increased, while Acidobacteria and Ascomycota decreased. Beneficial microbes such as Arthrobacter, Azoarcus, Bacillus, Paenibacillus, Pseudomonas, and Streptomyces thrived in the normal field, potentially serving as biomarkers for favorable soil conditions. Conversely, phytopathogens and growth-inhibiting bacteria were prevalent in the periodic waterlogged field, indicating unfavorable conditions. The co-occurrence network in rhizosphere of the normal field had the highest complexity, implying increased sharing of resources among microorganisms and enhanced soil biological fertility. Altogether, this study demonstrated that the periodic waterlogged field had a long-term negative effect on the soil microbial community which is a key determining factor of sugarcane growth.

Complete genome sequence of Pseudomonas aeruginosa PA99 clinical isolate from Thailand carrying two novel class 1 integrons, In2083 and In2084.

OBJECTIVES: The aim of this study was to identify and characterize multidrug resistance genes and the genetic contexts of integrons found in extensively drug resistant (XDR) Pseudomonas aeruginosa PA99 clinical isolate from Thailand. METHODS: The sequencing of P. aeruginosa PA99 genomic DNA was done by using Pacific Biosciences RS II sequencing platform. The generated reads were de novo assembled by Canu version 1.4 and the annotation was performed using Prokka v1.12b. The complete genome sequence was subjected for identification of sequence type, serotype, integrons, and antimicrobial resistance genes by MLST 2.0, PAst 1.0, INTEGRALL, Resfinder 4.1, and CARD 3.2.5, respectively. RESULTS: Pseudomonas aeruginosa PA99 genome consisted of a 6,946,480-bp chromosomal DNA with 65.9% GC and belonged to ST964 and serotype O4. Twenty-one antimicrobial resistance genes conferring XDR phenotype were identified. Of special note were carbapenem resistance genes (blaIMP-1, blaPAO, blaOXA-21, and blaOXA-396) and colistin resistance gene basR with L71R mutation. Integron analysis revealed that P. aeruginosa PA99 harbored five class 1 integrons: two copies of In994 (blaIMP-1), an In1575 (aadB), and two novel integrons, In2083 (blaOXA-21 - aac(6')-Ib3 - aac(6')-Ib-cr - ere(A)1∆2 - dfrA1r) and In2084 (blaIMP-1 - aac(6')-Ib3 - aac(6')-Ib-cr). CONCLUSIONS: To the best of our knowledge, this is the first report of two novel class I integrons designated by INTEGRALL as In2083 and In2084 found in XDR-P. aeruginosa PA99 clinical isolate from Thailand. The characterization of genetic contexts of In2083 and In2084 provide the evidence of the assorting of resistance genes to evolve as novel integrons.

Insights into the genome of Methylobacterium sp. NMS14P, a novel bacterium for growth promotion of maize, chili, and sugarcane.

A novel methylotrophic bacterium designated as NMS14P was isolated from the root of an organic coffee plant (Coffea arabica) in Thailand. The 16S rRNA sequence analysis revealed that this new isolate belongs to the genus Methylobacterium, and its novelty was clarified by genomic and comparative genomic analyses, in which NMS14P exhibited low levels of relatedness with other Methylobacterium-type strains. NMS14P genome consists of a 6,268,579 bp chromosome, accompanied by a 542,519 bp megaplasmid and a 66,590 bp plasmid, namely pNMS14P1 and pNMS14P2, respectively. Several genes conferring plant growth promotion are aggregated on both chromosome and plasmids, including phosphate solubilization, indole-3-acetic acid (IAA) biosynthesis, cytokinins (CKs) production, 1-aminocyclopropane-1-carboxylate (ACC) deaminase activity, sulfur-oxidizing activity, trehalose synthesis, and urea metabolism. Furthermore, pangenome analysis showed that NMS14P possessed the highest number of strain-specific genes accounting for 1408 genes, particularly those that are essential for colonization and survival in a wide array of host environments, such as ABC transporter, chemotaxis, quorum sensing, biofilm formation, and biosynthesis of secondary metabolites. In vivo tests have supported that NMS14P significantly promoted the growth and development of maize, chili, and sugarcane. Collectively, NMS14P is proposed as a novel plant growth-promoting Methylobacterium that could potentially be applied to a broad range of host plants as Methylobacterium-based biofertilizers to reduce and ultimately substitute the use of synthetic agrochemicals for sustainable agriculture.

Chitooligosaccharide prevents vascular endothelial cell apoptosis by attenuation of endoplasmic reticulum stress via suppression of oxidative stress through Nrf2-SOD1 up-regulation.

CONTEXT: Endoplasmic reticulum (ER) stress contributes to endothelium pathological conditions. Chitooligosaccharides (COS) have health benefits, but their effect on endothelial cells is unknown. We demonstrate for the first time a protective effect of COS against ER-induced endothelial cell damage. OBJECTIVE: To evaluate the protective effect of COS on ER stress-induced apoptosis in endothelial cells. MATERIAL AND METHODS: Endothelial (EA.hy926) cells were pre-treated with COS (250 or 500 µg/mL) for 24 h, and then treated with 0.16 µg/mL of Tg for 24 h and compared to the untreated control. Apoptosis and necrosis were detected by Annexin V-FITC/propidium iodide co-staining. Reactive oxygen species (ROS) were measured with the DCFH2-DA and DHE probes. The protective pathway and ER stress markers were evaluated by reverse transcription-polymerase chain reaction, western blot, and immunofluorescence analyses. RESULTS: COS attenuated ER stress-induced cell death. The viability of EA.hy926 cells treated with Tg alone was 44.97 ± 1% but the COS pre-treatment increased cells viability to 74.74 ± 3.95% in the 250 µg/mL COS and 75.34 ± 2.4% in the 500 µg/mL COS treatments. Tg induced ER stress and ROS, which were associated with ER stress-mediated death. Interestingly, COS reduced ROS by upregulating nuclear factor-E2-related factor 2 (Nrf2), and the oxidative enzymes, superoxide dismutase1 (SOD1) and catalase. COS also suppressed up-regulation of the ER-related apoptosis protein, CHOP induced by Tg. CONCLUSIONS: COS protected against ER stress-induced apoptosis in endothelial cells by suppressing ROS and up-regulation Nrf2 and SOD1. These findings support the use of COS to protect endothelial cells.

Investigation of mechanisms underlying the inhibitory effects of metformin against proliferation and growth of neuroblastoma SH-SY5Y cells.

Besides being anti-diabetic drug, metformin also has anti-proliferation and growth in several tumors; however, details of possible mechanism have not been elucidated. Here, we investigated the effects of metformin in neuroblastoma which has been termed as extra-cranial solid tumor that is due to a differentiation block with more stemness. The results showed that 5 mM metformin inhibited cell cycle progression at G0/G1 phase. Metformin also induced morphological differentiation of neuroblastoma into neuron-like phenotypes by which upregulation of MAP2, ß-tubulin III and tyrosine hydroxylase expressions with no significant difference to retinoic acid (RA)-treated cells. We also tested proliferative, growth and self-renewal ability after neuroblastoma being differentiated by metformin for 24 h. The proliferative rate, sizes and numbers of colonies and spheroids were significantly reduced in differentiated neuroblastoma compared to undifferentiated neuroblastoma. A significant increase of ROS and ADP/ATP ratio with decreased mitochondrial membrane potential (MMP) were observed in metformin-treated cells, indicating mitochondrial biogenesis and metabolic change during metformin-mediated differentiation. The further studies exhibited that p-Erk1/2 and Cdk5 levels were reduced in metformin treatment whereas using PD98095 and roscovitine, selectively inhibited Erk1/2 and Cdk5, respectively, significantly increased neurite length and MAP2 expression. In addition, cell proliferation was decreased by cell cycle arrested at G0/G1 phase. Taken together, this study suggests the inhibitory effects of metformin against proliferation and growth of neuroblastoma due to induced morphological differentiation may be through Erk1/2 and Cdk5 pathways. Therefore, metformin might be eventually considered as a differentiation agent for neuroblastoma treatment in term of differentiation therapy.

Comparative Metagenomics Reveals Microbial Signatures of Sugarcane Phyllosphere in Organic Management.

Converting conventional farms to organic systems to improve ecosystem health is an emerging trend in recent decades, yet little is explored to what extent and how this process drives the taxonomic diversity and functional capacity of above-ground microbes. This study was, therefore, conducted to investigate the effects of agricultural management, i.e., organic, transition, and conventional, on the structure and function of sugarcane phyllosphere microbial community using the shotgun metagenomics approach. Comparative metagenome analysis exhibited that farming practices strongly influenced taxonomic and functional diversities, as well as co-occurrence interactions of phyllosphere microbes. A complex microbial network with the highest connectivity was observed in organic farming, indicating strong resilient capabilities of its microbial community to cope with the dynamic environmental stressors. Organic farming also harbored genus Streptomyces as the potential keystone species and plant growth-promoting bacteria as microbial signatures, including Mesorhizobium loti, Bradyrhizobium sp. SG09, Lactobacillus plantarum, and Bacillus cellulosilyticus. Interestingly, numerous toxic compound-degrading species were specifically enriched in transition farming, which might suggest their essential roles in the transformation of conventional to organic farming. Moreover, conventional practice diminished the abundance of genes related to cell motility and energy metabolism of phyllosphere microbes, which could negatively contribute to lower microbial diversity in this habitat. Altogether, our results demonstrated the response of sugarcane-associated phyllosphere microbiota to specific agricultural managements that played vital roles in sustainable sugarcane production.

Suppressing Cdk5 Activity by Luteolin Inhibits MPP+-Induced Apoptotic of Neuroblastoma through Erk/Drp1 and Fak/Akt/GSK3ß Pathways.

Parkinson's disease (PD) is characterized by the progressive degeneration of dopaminergic neurons. The cause of PD is still unclear. Oxidative stress and mitochondrial dysfunction have been linked to the development of PD. Luteolin, a non-toxic flavonoid, has become interested in an alternative medicine, according to its effects on anti-oxidative stress and anti-apoptosis, although the underlying mechanism of luteolin on PD has not been fully elucidated. This study aims to investigate whether luteolin prevents neurotoxicity induction by 1-methyl-4-phenylpyridinium iodide (MPP+), a neurotoxin in neuroblastoma SH-SY5Y cells. The results reveal that luteolin significantly improved cell viability and reduced apoptosis in MPP+-treated cells. Increasing lipid peroxidation and superoxide anion (O2-), including mitochondrial membrane potential (Δψm) disruption, is ameliorated by luteolin treatment. In addition, luteolin attenuated MPP+-induced neurite damage via GAP43 and synapsin-1. Furthermore, Cdk5 is found to be overactivated and correlated with elevation of cleaved caspase-3 activity in MPP+-exposed cells, while phosphorylation of Erk1/2, Drp1, Fak, Akt and GSK3ß are inhibited. In contrast, luteolin attenuated Cdk5 overactivation and supported phosphorylated level of Erk1/2, Drp1, Fak, Akt and GSK3ß with reducing in cleaved caspase-3 activity. Results indicate that luteolin exerts neuroprotective effects via Cdk5-mediated Erk1/2/Drp1 and Fak/Akt/GSK3ß pathways, possibly representing a potential preventive agent for neuronal disorder.

Enrichment and characterization of bacterial consortia for degrading 2-mercaptobenzothiazole in rubber industrial wastewater.

Benzothiazoles especially 2-mercaptobenzothiazole (2-MBT) in rubber industrial wastewater can be released into the environment. They can cause adverse health impacts. This study aimed to obtain efficient 2-MBT-degrading bacteria for wastewater application. The bacterial consortia were enriched by incubating rubber wastewater sludge in a medium containing 2-MBT for 28 days. Stepwise acclimatization was conducted with increasing 2-MBT concentrations from 50 to 200 mg L-1 in nitrogen-containing medium for 76 days. The process significantly increased the bacterial number and changed the dominant populations. Among these consortia, the EN consortium from benzothiazole-containing sludge had the highest specific 2-MBT biodegradation rate of 5.2 ± 0.5 mg L-1 day-1 mg protein-1 and could degrade up to 300 mg L-1 2-MBT. From 16S rRNA gene analysis, Pseudomonas was the dominant genus at approximately 70 % of the total population. Stenotrophomonas was the second most abundant populations and have never been reported for 2-MBT biodegradation. The EN consortium removed 65-79 % and 90-93 % of 112 mg L-1 2-MBT and ∼4000 mg L-1 COD in rubber wastewater, respectively, which were significantly higher than the values of natural attenuation. Therefore, the EN consortium could be an ideal inoculum for the post-treatment of benzothiazoles in rubber industrial wastewater.

Diverse Microbial Community Profiles of Propionate-Degrading Cultures Derived from Different Sludge Sources of Anaerobic Wastewater Treatment Plants.

Anaerobic digestion (AD) has been used for wastewater treatment and production of renewable energy or biogas. Propionate accumulation is one of the important problems leading to an unstable system and low methane production. Revealing propionate-degrading microbiome is necessary to gain a better knowledge for alleviation of the problem. Herein, we systematically investigated the propionate-degrading cultures enriched from various anaerobic sludge sources of agro-industrial wastewater treatment plants using 16S rRNA gene sequencing. Different microbial profiles were shown even though the methanogenic activities of all cultures were similar. Interestingly, non-classical propionate-degrading key players Smithella, Syntrophomonas, and Methanosaeta were observed as common prevalent taxa in our enriched cultures. Moreover, different hydrogenotrophic methanogens were found specifically to the different sludge sources. The enriched culture of high salinity sludge showed a distinct microbial profile compared to the others, containing mainly Thermovirga, Anaerolinaceae, Methanosaeta, Syntrophobactor, and Methanospirillum. Our microbiome analysis revealed different propionate-degrading community profiles via mainly the Smithella pathway and offers inside information for microbiome manipulation in AD systems to increase biogas production corresponding to their specific microbial communities.

Type III secretion system confers enhanced virulence in clinical non-O1/non-O139 Vibrio cholerae.

Vibrio cholerae O1 infections mainly are responsible for significant mortality and morbidity amongst children, however, non-O1/non-O139 V. cholerae have also been reported to cause mild to severe infections because of their virulence potential. The pathogenic mechanisms of non-O1, non-O139 isolates are not as clearly understood as for that of O1 and O139 isolates. Type three secretion system (TTSS) is also considered one of the important virulent factors and during the current study, we investigated the role of TTSS in association with non-O1/non-O139 clinical isolates. We report that the presence of TTSS in non-O1/non-O139 V. cholerae clinical isolate (D13) from a child confers more virulence compared to the one lacking it (D15) in another clinical case during the small cholera epidemic. Moreover, the antibiotic susceptibility profiles of D13 and D15 indicate that they are multiple drug resistance (MDR) isolates. The sequence analysis for TTSS cluster was carried out for D13 and compared with the TTSS positive reference Vibrio parahaemolyticus RIMD2210633 and V. cholerae AM19226 non-O1/non-O139. Furthermore, the pathogenic potential of D13 & D15 was also explored in simple and economical invertebrate host model, Galleria mellonella and the results revealed that TTSS+ve isolate (D13) was more virulent compared to TTSS-ve isolate (D15). We suggest that this distinct genetic difference, seen in natural variants D13 and D15, is also reflected by the clinical picture of the former in contributing towards the severity of disease symptoms and this finding was further validated by assessing virulence potential of both isolates using inexpensive G. mellonella infection model.

Draft Genome Sequence of the Wood-Decaying Fungus Xylaria sp. BCC 1067.

Xylaria sp. BCC 1067 is a wood-decaying fungus which is capable of producing lignocellulolytic enzymes. Based on the results of a single-molecule real-time sequencing technology analysis, we present the first draft genome of Xylaria sp. BCC 1067, comprising 54.1 Mb with 12,112 protein-coding genes.

Complete Genome Sequence of Halocella sp. Strain SP3-1, an Extremely Halophilic, Glycoside Hydrolase- and Bacteriocin-Producing Bacterium Isolated from a Salt Evaporation Pond.

Halocella sp. strain SP3-1, a cellulose-degrading bacterium, was isolated from a hypersaline evaporation pond in Thailand. Here, we report the first complete genome sequence of strain SP3-1. This species has a genome size of 4,035,760 bases, and the genome contains several genes encoding cellulose, hemicellulose, starch-degrading enzymes, and bacteriocins.

An Improved Genome-Scale Metabolic Model of Arthrospira platensis C1 (iAK888) and Its Application in Glycogen Overproduction.

Glycogen-enriched biomass of Arthrospira platensis has increasingly gained attention as a source for bioethanol production. To study the metabolic capabilities of glycogen production in A. platensis C1, a genome-scale metabolic model (GEM) could be a useful tool for predicting cellular behavior and suggesting strategies for glycogen overproduction. New experimentally validated GEM of A. platensis C1 namely iAK888, which has improved metabolic coverage and functionality was employed in this research. The iAK888 is a fully functional compartmentalized GEM consisting of 888 genes, 1,096 reactions, and 994 metabolites. This model was demonstrated to reasonably predict growth and glycogen fluxes under different growth conditions. In addition, iAK888 was further employed to predict the effect of deficiencies of NO3-, PO43-, or SO42- on the growth and glycogen production in A. platensis C1. The simulation results showed that these nutrient limitations led to a decrease in growth flux and an increase in glycogen flux. The experiment of A. platensis C1 confirmed the enhancement of glycogen fluxes after the cells being transferred from normal Zarrouk's medium to either NO3-, PO43-, or SO42--free Zarrouk's media. Therefore, iAK888 could be served as a predictive model for glycogen overproduction and a valuable multidisciplinary tool for further studies of this important academic and industrial organism.

Culture degeneration in conidia of Beauveria bassiana and virulence determinants by proteomics.

The quality of Beauveria bassiana conidia directly affects the virulence against insects. In this study, continuous subculturing of B. bassiana on both rice grains and potato dextrose agar (PDA) resulted in 55 and 49 % conidial yield reduction after 12 passages and 68 and 60 % virulence reduction after 20 and 12 passages at four d post-inoculation, respectively. The passage through Tenebrio molitor and Spodoptera exigua restored the virulence of rice and PDA subcultures, respectively. To explore the molecular mechanisms underlying the conidial quality and the decline of virulence after multiple subculturing, we investigated the conidial proteomic changes. Successive subculturing markedly increased the protein levels in oxidative stress response, autophagy, amino acid homeostasis, and apoptosis, but decreased the protein levels in DNA repair, ribosome biogenesis, energy metabolism, and virulence. The nitro blue tetrazolium assay verified that the late subculture's colony and conidia had a higher oxidative stress level than the early subculture. A 2A-type protein phosphatase and a Pleckstrin homology domain protein Slm1, effector proteins of the target of rapamycin (TOR) complex 1 and 2, respectively, were dramatically increased in the late subculture. These results suggest that TOR signalling might be associated with ageing in B. bassiana late subculture, in turn affecting its physiological characteristics and virulence.

Exploring Components of the CO2-Concentrating Mechanism in Alkaliphilic Cyanobacteria Through Genome-Based Analysis.

In cyanobacteria, the CO2-concentrating mechanism (CCM) is a vital biological process that provides effective photosynthetic CO2 fixation by elevating the CO2 level near the active site of Rubisco. This process enables the adaptation of cyanobacteria to various habitats, particularly in CO2-limited environments. Although CCM of freshwater and marine cyanobacteria are well studied, there is limited information on the CCM of cyanobacteria living under alkaline environments. Here, we aimed to explore the molecular components of CCM in 12 alkaliphilic cyanobacteria through genome-based analysis. These cyanobacteria included 6 moderate alkaliphiles; Pleurocapsa sp. PCC 7327, Synechococcus spp., Cyanobacterium spp., Spirulina subsalsa PCC 9445, and 6 strong alkaliphiles (i.e. Arthrospira spp.). The results showed that both groups belong to ß-cyanobacteria based on ß-carboxysome shell proteins with form 1B of Rubisco. They also contained standard genes, ccmKLMNO cluster, which is essential for ß-carboxysome formation. Most strains did not have the high-affinity Na+/HCO3- symporter SbtA and the medium-affinity ATP-dependent HCO3- transporter BCT1. Specifically, all strong alkaliphiles appeared to lack BCT1. Beside the transport systems, carboxysomal ß-CA, CcaA, was absent in all alkaliphiles, except for three moderate alkaliphiles: Pleurocapsa sp. PCC 7327, Cyanobacteriumstranieri PCC 7202, and Spirulina subsalsa PCC 9445. Furthermore, comparative analysis of the CCM components among freshwater, marine, and alkaliphilic ß-cyanobacteria revealed that the basic molecular components of the CCM in the alkaliphilic cyanobacteria seemed to share more degrees of similarity with freshwater than marine cyanobacteria. These findings provide a relationship between the CCM components of cyanobacteria and their habitats.

Cyanobacterial Biofuels: Strategies and Developments on Network and Modeling.

Cyanobacteria, the phototrophic microorganisms, have attracted much attention recently as a promising source for environmentally sustainable biofuels production. However, barriers for commercial markets of cyanobacteria-based biofuels concern the economic feasibility. Miscellaneous strategies for improving the production performance of cyanobacteria have thus been developed. Among these, the simple ad hoc strategies resulting in failure to optimize fully cell growth coupled with desired product yield are explored. With the advancement of genomics and systems biology, a new paradigm toward systems metabolic engineering has been recognized. In particular, a genome-scale metabolic network reconstruction and modeling is a crucial systems-based tool for whole-cell-wide investigation and prediction. In this review, the cyanobacterial genome-scale metabolic models, which offer a system-level understanding of cyanobacterial metabolism, are described. The main process of metabolic network reconstruction and modeling of cyanobacteria are summarized. Strategies and developments on genome-scale network and modeling through the systems metabolic engineering approach are advanced and employed for efficient cyanobacterial-based biofuels production.

Draft genome sequence of Arthrospira platensis C1 (PCC9438).

Arthrospira platensis is a cyanobacterium that is extensively cultivated outdoors on a large commercial scale for consumption as a food for humans and animals. It can be grown in monoculture under highly alkaline conditions, making it attractive for industrial production. Here we describe the complete genome sequence of A. platensis C1 strain and its annotation. The A. platensis C1 genome contains 6,089,210 bp including 6,108 protein-coding genes and 45 RNA genes, and no plasmids. The genome information has been used for further comparative analysis, particularly of metabolic pathways, photosynthetic efficiency and barriers to gene transfer.

Proteome analysis at the subcellular level of the cyanobacterium Spirulina platensis in response to low-temperature stress conditions.

The present study addresses the differential expression of Spirulina platensis proteins detected during cold-induced stress, analyzed at the subcellular level. In performing differential expression analysis, the results revealed upregulated proteins in every subcellular fraction, including two-component response systems, DNA repair, molecular chaperones, stress-induced proteins and proteins involved in other biological processes such as secretion systems and nitrogen assimilation. The chlorophyll biosynthetic proteins, protochlorophyllide oxidoreductase and ChlI, had unique expression patterns as detected in the thylakoid membrane; the levels of these proteins immediately decreased during the first 45 min of low-temperature exposure. In contrast, their expression levels significantly increased after low-temperature exposure, indicating the relevance of the chlorophyll biosynthesis in Spirulina in response to low-temperature stress in the light condition. In addition, this is the first report in which genome-based protein identification in S. platensis by peptide mass fingerprinting was performed using the database derived from the unpublished Spirulina genome sequence.

A combined stress response analysis of Spirulina platensis in terms of global differentially expressed proteins, and mRNA levels and stability of fatty acid biosynthesis genes.

Changes in gene expression play a critical role in enhancing the ability of cyanobacteria to survive under cold conditions. In the present study, Spirulina platensis cultures were grown at the optimal growth temperature, in the light, before being transferred to dark conditions at 22 degrees C. Two dimensional-differential gel electrophoresis was then performed to separate differentially expressed proteins that were subsequently identified by MS. Among all differentiated proteins identified, a protein involved in fatty acid biosynthesis, (3R)-hydroxymyristoyl-[acyl-carrier-protein]-dehydratase encoded by fabZ, was the most up-regulated protein. However, the fatty-acid desaturation proteins were not significantly differentiated. This raised the question of how the unsaturated fatty acid, especially gamma-linolenic acid, content in the cells in the cold-dark shift remained stable compared with that of the cold shift. Thus, a study at the transcriptional level of these desaturase genes, desC, desA and desD, and also of the fabZ gene was conducted. The results indicated that in the dark, where energy is limited, mRNA stability was enhanced by exposure to low temperatures. The data demonstrate that when the cells encounter cold stress with energy limitation, they can maintain their homeoviscous adaptation ability via mRNA stability.

Revealing differentially expressed proteins in two morphological forms of Spirulina platensis by proteomic analysis.

Spirulina is distinguished from other cyanobacteria by its spiral morphology; however, this cyanobacterium has frequently been observed with a linear morphology in laboratory and industrial conditions. In our laboratory conditions, the simultaneously presence of the linear and spiral forms has also been observed. In the present study, the two forms of S. platensis C1 were separated and grown as axenic cultures in order to study the proteins that were differentially expressed in the soluble and insoluble protein fractions of the spiral and the linear forms. Two dimensional-differential gel electrophoresis (2D-DIGE) was performed to separate differentially expressed proteins that were subsequently identified by mass spectrometry. The differentially expressed proteins suggested two points. First, the morphological change is possibly induced by various environmental stresses such as oxygen level, carbon dioxide level, nutrient availability, and light. Second, the change of cell-shape might be a result of the change in a cell shape determination mechanism. Thus, this study is the first to show evidence at the protein level that may explain this morphological transformation in Spirulina.