Salibaculum halophilum gen. nov., sp. nov. and Salibaculum griseiflavum sp. nov., in the family Rhodobacteraceae.

Two Gram-stain-negative, moderately halophilic, non-motile, rod-shaped, pale yellow, and aerobic strains, designated WDS1C4T and WDS4C29T, were isolated from a marine solar saltern in Weihai, Shandong Province, PR China. Growth of strain WDS1C4T occurred at 10-45 °C (optimum, 37 °C), with 4-16 % (w/v) NaCl (optimum, 8 %) and at pH 6.5-9.0 (optimum, pH 7.5). Growth of strain WDS4C29T occurred at 10-45 °C (optimum, 40 °C), with 2-18 % (w/v) NaCl (optimum, 6 %) and at pH 6.5-9.0 (optimum, pH 7.5). Q-10 was the sole respiratory quinone of the two strains. The major polar lipids of strains WDS1C4T and WDS4C29T were phosphatidylglycerol, phosphatidylethanolamine and phosphatidylcholine. The major cellular fatty acid in strains WDS1C4T and WDS4C29T was C18 : 1 ω7c, and the genomic DNA G+C contents of strains WDS1C4T and WDS4C29T were 67.6 and 63.3 mol%, respectively. Phylogenetic analyses based on 16S rRNA gene sequences indicated that strains WDS1C4T and WDS4C29T were members of the family Rhodobacteraceae and showed 94.3 and 95.3 % similarities to their closest relative, Celeribacter indicus, respectively. The similarity between WDS1C4T and WDS4C29T was 97.3 %. Differential phenotypic and genotypic characteristics of the two isolates from recognized genera showed that the two strains should be classified as representing two novel species in a new genus for which the names Salibaculum halophilum gen. nov., sp. nov. (type species, type strain WDS1C4T=MCCC 1H00179T=KCTC 52542T) and Salibaculum griseiflavum sp. nov. (WDS4C29T=MCCC 1H00175T=KCTC 52541T) are proposed.

Transcriptional and metabolic response against hydroxyethane-(1,1-bisphosphonic acid) on bacterial denitrification by a halophilic Pannonibacter sp. strain DN.

Biological denitrification is an environmentally sound pathway for the elimination of nitrogen pollution in wastewater treatment. Extreme environmental conditions, such as the co-existence of toxic organic pollutants, can affect biological denitrification. However, the potential underlying mechanism remains largely unexplored. Herein, the effect of a model pollutant, hydroxyethane-(1,1-bisphosphonic acid) (HEDP), a widely applied and consumed bisphosphonate, on microbial denitrification was investigated by exploring the metabolic and transcriptional responses of an isolated denitrifier, Pannonibacter sp. strain DN. Results showed that nitrate removal efficiency decreased from 85% to 50% with an increase in HEDP concentration from 0 to 3.5 mM, leading to nitrite accumulation of 204 mg L-1 in 3.5 mM HEDP. This result was due to the lower bacterial population count and reduction in the live cell percentage. Further investigation revealed that HEDP caused a decrease in membrane potential from 0.080 ±â€¯0.005 to 0.020 ±â€¯0.002 with the increase in HEDP from 0 to 3.5 mM. This hindered electron transfer, which is required for nitrate transformation into nitrogen gas. Moreover, transcriptional profiling indicated that HEDP enhanced the genes involved in ROS (O2-) scavenging, thus protecting cells against oxidative stress damage. However, the suppression of genes responsible for the production of NADH/FADH2 in tricarboxylic acid cycle (TCA), NADH catalyzation (NADH dehydrogenase) in (electron transport chain) ETC system and denitrifying genes, especially nor and nir, in response to 2.5 mM HEDP were identified as the key factor inhibiting transfer of electron from TCA cycle to denitrifying enzymes through ETC system.

Ecological impact of the antibiotic ciprofloxacin on microbial community of aerobic activated sludge.

This study investigated the effects and fate of the antibiotic ciprofloxacin (CIP) at environmentally relevant levels (50-500 µg/L) in activated sludge (AS) microbial communities under aerobic conditions. Exposure to 500 µg/L of CIP decreased species diversity by about 20% and significantly altered the phylogenetic structure of AS communities compared to those of control communities (no CIP exposure), while there were no significant changes upon exposure to 50 µg/L of CIP. Analysis of community composition revealed that exposure to 500 µg/L of CIP significantly reduced the relative abundance of Rhodobacteraceae and Nakamurellaceae by more than tenfold. These species frequently occur in AS communities across many full-scale wastewater treatment plants and are involved in key ecosystem functions (i.e., organic matter and nitrogen removal). Our analyses showed that 50-500 µg/L CIP was poorly removed in AS (about 20% removal), implying that the majority of CIP from AS processes may be released with either their effluents or waste sludge. We therefore strongly recommend further research on CIP residuals and/or post-treatment processes (e.g., anaerobic digestion) for waste streams that may cause ecological risks in receiving water bodies.

H-Aquil: a chemically defined cell culture medium for trace metal studies in Vibrios and other marine heterotrophic bacteria.

A variety of trace metals, including prominently iron (Fe) are necessary for marine microorganisms. Chemically defined medium recipes have been used for several decades to study phytoplankton, but similar methods have not been adopted as widely in studies of marine heterotrophic bacteria. Medium recipes for these organisms frequently include tryptone, casamino acids, as well as yeast and animal extracts. These components introduce unknown concentrations of trace elements and organic compounds, complicating metal speciation. Minimal medium recipes utilizing known carbon and nitrogen sources do exist but often have high background trace metal concentrations. Here we present H-Aquil, a version of the phytoplankton medium Aquil adapted for marine heterotrophic bacteria. This medium consists of artificial seawater supplemented with a carbon source, phosphate, amino acids, and vitamins. As in Aquil, trace metals are controlled using the synthetic chelator EDTA. We also address concerns of EDTA toxicity, showing that concentrations up to 100 µM EDTA do not lead to growth defects in the copiotrophic bacterium Vibrio harveyi or the oligotrophic bacterium Candidatus Pelagibacter ubique HTCC1062, a member of the SAR11 clade. H-Aquil is used successfully to culture species of Vibrio, Phaeobacter, and Silicibacter, as well as several environmental isolates. We report a substantial decrease in growth rate between cultures grown with or without added Fe, making the medium suitable for conducting Fe-limitation studies in a variety of marine heterotrophic bacteria.

Multi-omics response of Pannonibacter phragmitetus BB to hexavalent chromium.

The release of hexavalent chromium [Cr(VI)] into water bodies poses a major threat to the environment and human health. However, studies of the biological response to Cr(VI) are limited. In this study, a toxic bacterial mechanism of Cr(VI) was investigated using Pannonibacter phragmitetus BB (hereafter BB), which was isolated from chromate slag. The maximum Cr(VI) concentrations with respect to the resistance and reduction by BB are 4000 mg L-1 and 2500 mg L-1, respectively. In the BB genome, more genes responsible for Cr(VI) resistance and reduction are observed compared with other P. phragmitetus strains. A total of 361 proteins were upregulated to respond to Cr(VI) exposure, including enzymes for Cr(VI) uptake, intracellular reduction, ROS detoxification, DNA repair, and Cr(VI) efflux and proteins associated with novel mechanisms involving extracellular reduction mediated by electron transfer, quorum sensing, and chemotaxis. Based on metabolomic analysis, 174 metabolites were identified. Most of the upregulated metabolites are involved in amino acid, glucose, lipid, and energy metabolisms. The results show that Cr(VI) induces metabolite production, while metabolites promote Cr(VI) reduction. Overall, multi-enzyme expression and metabolite production by BB contribute to its high ability to resist/reduce Cr(VI). This study provides details supporting the theory of Cr(VI) reduction and a theoretical basis for the efficient bioremoval of Cr(VI) from the environment.

Paenialvin A-D, four peptide antibiotics produced by Paenibacillus alvei DSM 29.

Four peptide antibiotics, named paenialvin A-D, were isolated from Paenibacillus alvei DSM 29. Mass spectrum analysis determined the molecular masses of paenialvin A-D to be 1891, 1875, 1877, and 1923 Da, respectively. Tandem mass spectra and nuclear magnetic resonance (NMR) were used to elucidate their chemical structures. Paenialvin A-D showed antimicrobial activity against most strains that were tested, including methicillin-resistant Staphalococcus aureus, Staphylococcus aureus, Bacillus subtilis, Loktanella hongkongensis, Escherichia coli, and Pseudomonas aeruginosa. In particular, the minimum inhibitory concentration of paenialvins against Staphalococcus aureus reached 0.8-3.2 µg/mL. Although they were cytotoxic against HeLa cells at a concentration of 50 µg/mL, the lack of hemolysis by paenialvins confirmed that they are potential candidates for anti-tumor drugs.

Analysis of resistance genes of clinical Pannonibacter phragmitetus strain 31801 by complete genome sequencing.

To clarify the resistance mechanisms of Pannonibacter phragmitetus 31801, isolated from the blood of a liver abscess patient, at the genomic level, we performed whole genomic sequencing using a PacBio RS II single-molecule real-time long-read sequencer. Bioinformatic analysis of the resulting sequence was then carried out to identify any possible resistance genes. Analyses included Basic Local Alignment Search Tool searches against the Antibiotic Resistance Genes Database, ResFinder analysis of the genome sequence, and Resistance Gene Identifier analysis within the Comprehensive Antibiotic Resistance Database. Prophages, clustered regularly interspaced short palindromic repeats (CRISPR), and other putative virulence factors were also identified using PHAST, CRISPRfinder, and the Virulence Factors Database, respectively. The circular chromosome and single plasmid of P. phragmitetus 31801 contained multiple antibiotic resistance genes, including those coding for three different types of ß-lactamase [NPS ß-lactamase (EC 3.5.2.6), ß-lactamase class C, and a metal-dependent hydrolase of ß-lactamase superfamily I]. In addition, genes coding for subunits of several multidrug-resistance efflux pumps were identified, including those targeting macrolides (adeJ, cmeB), tetracycline (acrB, adeAB), fluoroquinolones (acrF, ceoB), and aminoglycosides (acrD, amrB, ceoB, mexY, smeB). However, apart from the tripartite macrolide efflux pump macAB-tolC, the genome did not appear to contain the complete complement of subunit genes required for production of most of the major multidrug-resistance efflux pumps.

Genomic insights of Pannonibacter phragmitetus strain 31801 isolated from a patient with a liver abscess.

Pannonibacter phragmitetus is a bioremediation reagent for the detoxification of heavy metals and polycyclic aromatic compounds (PAHs) while it rarely infects healthy populations. However, infection by the opportunistic pathogen P. phragmitetus complicates diagnosis and treatments, and poses a serious threat to immunocompromised patients owing to its multidrug resistance. Unfortunately, genome features, antimicrobial resistance, and virulence potentials in P. phragmitetus have not been reported before. A predominant colony (31801) was isolated from a liver abscess patient, indicating that it accounted for the infection. To investigate its infection mechanism(s) in depth, we sequenced this bacterial genome and tested its antimicrobial resistance. Average nucleotide identity (ANI) analysis assigned the bacterium to the species P. phragmitetus (ANI, >95%). Comparative genomics analyses among Pannonibacter spp. representing the different living niches were used to describe the Pannonibacter pan-genomes and to examine virulence factors, prophages, CRISPR arrays, and genomic islands. Pannonibacter phragmitetus 31801 consisted of one chromosome and one plasmid, while the plasmid was absent in other Pannonibacter isolates. Pannonibacter phragmitetus 31801 may have a great infection potential because a lot of genes encoding toxins, flagellum formation, iron uptake, and virulence factor secretion systems in its genome. Moreover, the genome has 24 genomic islands and 2 prophages. A combination of antimicrobial susceptibility tests and the detailed antibiotic resistance gene analysis provide useful information about the drug resistance mechanisms and therefore can be used to guide the treatment strategy for the bacterial infection.

Tungsten accumulation by highly tolerant marine hydrothermal Sulfitobacter dubius strains carrying a tupBCA cluster.

Tungsten (W) has industrial and economic importance, and is in the European Union list of metals with a high supply risk. It is used by living organisms, which transport it into the cell, in the form of tungstate ion (WO42-), using three different ABC-type transporters from the specific W-uptake system coded by tupABC gene cluster. In this study, strains from a collection recovered from deep-sea hydrothermal sediments were selected according to their ability to tolerate metals and to possess the tup genetic determinants. Three multimetal-tolerant strains, Sulfitobacter dubius NA4, As(V)4 and Sb5, were chosen. The strains were able to grow in the presence of high tungsten concentrations and their growth was unaffected by 1mM tungsten. Moreover, strain Sb5 was able to accumulate up to 52µg W mg-1 protein. Their tup genes were shown to be organized as tupBCA, which is not the most usual gene arrangement. All three strains had the classical TupA conserved motif TTTS, comprising a first Thr replaced by a Val, which seems to be a common feature of the genus Sulfitobacter. This study was an important first step in the exploration of new biological strategies for recovering tungsten from natural or anthropogenic W-impacted environments.

The limits to growth - energetic burden of the endogenous antibiotic tropodithietic acid in Phaeobacter inhibens DSM 17395.

Phaeobacter inhibens DSM 17395, a model organism for marine Roseobacter group, was studied for its response to its own antimicrobial compound tropodithietic acid (TDA). TDA biosynthesis is encoded on the largest extrachromosomal element of P. inhibens, the 262 kb plasmid, whose curation leads to an increased growth and biomass yield. In this study, the plasmid-cured strain was compared to the wild-type strain and to transposon mutants lacking single genes of the TDA biosynthesis. The data show that the growth inhibition of the wild-type strain can be mainly attributed to the TDA produced by P. inhibens itself. Oxygen uptake rates remained constant in all strains but the growth rate dropped in the wild-type which supports the recently proposed mode of TDA action. Metabolome analysis showed no metabolic alterations that could be attributed directly to TDA. Taken together, the growth of P. inhibens is limited by its own antibacterial compound due to a partial destruction of the proton gradient which leads to a higher energetic demand. The universal presence of TDA biosynthesis in genome-sequenced isolates of the genus Phaeobacter shows that there must be a high benefit of TDA for P. inhibens in its ecological niche despite the drawback on its metabolism.

Evidence for quorum sensing and differential metabolite production by a marine bacterium in response to DMSP.

Microbes, the foundation of the marine foodweb, do not function in isolation, but rather rely on molecular level interactions among species to thrive. Although certain types of interactions between autotrophic and heterotrophic microorganisms have been well documented, the role of specific organic molecules in regulating inter-species relationships and supporting growth are only beginning to be understood. Here, we examine one such interaction by characterizing the metabolic response of a heterotrophic marine bacterium, Ruegeria pomeroyi DSS-3, to growth on dimethylsulfoniopropionate (DMSP), an abundant organosulfur metabolite produced by phytoplankton. When cultivated on DMSP, R. pomeroyi synthesized a quorum-sensing molecule, N-(3-oxotetradecanoyl)-l-homoserine lactone, at significantly higher levels than during growth on propionate. Concomitant with the production of a quorum-sensing molecule, we observed differential production of intra- and extracellular metabolites including glutamine, vitamin B2 and biosynthetic intermediates of cyclic amino acids. Our metabolomics data indicate that R. pomeroyi changes regulation of its biochemical pathways in a manner that is adaptive for a cooperative lifestyle in the presence of DMSP, in anticipation of phytoplankton-derived nutrients and higher microbial density. This behavior is likely to occur on sinking marine particles, indicating that this response may impact the fate of organic matter.

Nitric Oxide Mediates Biofilm Formation and Symbiosis in Silicibacter sp. Strain TrichCH4B.

UNLABELLED: Nitric oxide (NO) plays an important signaling role in all domains of life. Many bacteria contain a heme-nitric oxide/oxygen binding (H-NOX) protein that selectively binds NO. These H-NOX proteins often act as sensors that regulate histidine kinase (HK) activity, forming part of a bacterial two-component signaling system that also involves one or more response regulators. In several organisms, NO binding to the H-NOX protein governs bacterial biofilm formation; however, the source of NO exposure for these bacteria is unknown. In mammals, NO is generated by the enzyme nitric oxide synthase (NOS) and signals through binding the H-NOX domain of soluble guanylate cyclase. Recently, several bacterial NOS proteins have also been reported, but the corresponding bacteria do not also encode an H-NOX protein. Here, we report the first characterization of a bacterium that encodes both a NOS and H-NOX, thus resembling the mammalian system capable of both synthesizing and sensing NO. We characterized the NO signaling pathway of the marine alphaproteobacterium Silicibacter sp. strain TrichCH4B, determining that the NOS is activated by an algal symbiont, Trichodesmium erythraeum. NO signaling through a histidine kinase-response regulator two-component signaling pathway results in increased concentrations of cyclic diguanosine monophosphate, a key bacterial second messenger molecule that controls cellular adhesion and biofilm formation. Silicibacter sp. TrichCH4B biofilm formation, activated by T. erythraeum, may be an important mechanism for symbiosis between the two organisms, revealing that NO plays a previously unknown key role in bacterial communication and symbiosis. IMPORTANCE: Bacterial nitric oxide (NO) signaling via heme-nitric oxide/oxygen binding (H-NOX) proteins regulates biofilm formation, playing an important role in protecting bacteria from oxidative stress and other environmental stresses. Biofilms are also an important part of symbiosis, allowing the organism to remain in a nutrient-rich environment. In this study, we show that in Silicibacter sp. strain TrichCH4B, NO mediates symbiosis with the alga Trichodesmium erythraeum, a major marine diazotroph. In addition, Silicibacter sp. TrichCH4B is the first characterized bacteria to harbor both the NOS and H-NOX proteins, making it uniquely capable of both synthesizing and sensing NO, analogous to mammalian NO signaling. Our study expands current understanding of the role of NO in bacterial signaling, providing a novel role for NO in bacterial communication and symbiosis.

L-sorbose is not only a substrate for 2-keto-L-gulonic acid production in the artificial microbial ecosystem of two strains mixed fermentation.

The co-culture system of the fermentation process of vitamin C can be regarded as an artificial microbial ecosystem (AME). To extend our understanding of this AME, an investigation of the relationship between strains, substrate and product was carried out in this study. The results showed that both Ketogulonicigenium vulgare and 2-keto-L-gulonic acid (2-KLG, the precursor of vitamin C) can inhibit the growth of the helper strain, while the helper strain promoted the growth of K. vulgare and 2-KLG production. Moreover, L-sorbose is not only a substrate for 2-KLG production in the AME, but also a promoter of K. vulgare and an inhibitor of the helper strain. In the earlier stage of fermentation, the inhibition of L-sorbose on the helper strain's growth is a key factor for ensuring an efficient fermentation. In the condition of adding the extra helper strain (OD: 0.57, ratio of inoculation: 2%), the yields of 2-KLG is increased by 9% in the 14% L-sorbose medium. To the best of our knowledge, this is the first report about the inhibition of substrate in the AME of 2-KLG production.

Intestinal microbiota and immune related genes in sea cucumber (Apostichopus japonicus) response to dietary ß-glucan supplementation.

ß-glucan is a prebiotic well known for its beneficial outcomes on sea cucumber health through modifying the host intestinal microbiota. High-throughput sequencing techniques provide an opportunity for the identification and characterization of microbes. In this study, we investigated the intestinal microbial community composition, interaction among species, and intestinal immune genes in sea cucumber fed with diet supplemented with or without ß-glucan supplementation. The results show that the intestinal dominant classes in the control group are Flavobacteriia, Gammaproteobacteria, and Alphaproteobacteria, whereas Alphaproteobacteria, Flavobacteriia, and Verrucomicrobiae are enriched in the ß-glucan group. Dietary ß-glucan supplementation promoted the proliferation of the family Rhodobacteraceae of the Alphaproteobacteria class and the family Verrucomicrobiaceae of the Verrucomicrobiae class and reduced the relative abundance of the family Flavobacteriaceae of Flavobacteria class. The ecological network analysis suggests that dietary ß-glucan supplementation can alter the network interactions among different microbial functional groups by changing the microbial community composition and topological roles of the OTUs in the ecological network. Dietary ß-glucan supplementation has a positive impact on immune responses of the intestine of sea cucumber by activating NF-κB signaling pathway, probably through modulating the balance of intestinal microbiota.

Exo-metabolome of Pseudovibrio sp. FO-BEG1 analyzed by ultra-high resolution mass spectrometry and the effect of phosphate limitation.

Oceanic dissolved organic matter (DOM) is an assemblage of reduced carbon compounds, which results from biotic and abiotic processes. The biotic processes consist in either release or uptake of specific molecules by marine organisms. Heterotrophic bacteria have been mostly considered to influence the DOM composition by preferential uptake of certain compounds. However, they also secrete a variety of molecules depending on physiological state, environmental and growth conditions, but so far the full set of compounds secreted by these bacteria has never been investigated. In this study, we analyzed the exo-metabolome, metabolites secreted into the environment, of the heterotrophic marine bacterium Pseudovibrio sp. FO-BEG1 via ultra-high resolution mass spectrometry, comparing phosphate limited with phosphate surplus growth conditions. Bacteria belonging to the Pseudovibrio genus have been isolated worldwide, mainly from marine invertebrates and were described as metabolically versatile Alphaproteobacteria. We show that the exo-metabolome is unexpectedly large and diverse, consisting of hundreds of compounds that differ by their molecular formulae. It is characterized by a dynamic recycling of molecules, and it is drastically affected by the physiological state of the strain. Moreover, we show that phosphate limitation greatly influences both the amount and the composition of the secreted molecules. By assigning the detected masses to general chemical categories, we observed that under phosphate surplus conditions the secreted molecules were mainly peptides and highly unsaturated compounds. In contrast, under phosphate limitation the composition of the exo-metabolome changed during bacterial growth, showing an increase in highly unsaturated, phenolic, and polyphenolic compounds. Finally, we annotated the detected masses using multiple metabolite databases. These analyses suggested the presence of several masses analogue to masses of known bioactive compounds. However, the annotation was successful only for a minor part of the detected molecules, underlining the current gap in knowledge concerning the biosynthetic ability of marine heterotrophic bacteria.

Pelagicola litorisediminis sp. nov., a novel alphaproteobacterium isolated from tidal flat sediment.

A Gram-negative, aerobic, non-motile and rod-shaped or ovoid bacterial strain, designated D1-W8(T), was isolated from a tidal flat on the South Sea in South Korea. Strain D1-W8(T) was found to grow optimally at 25 °C, at pH 7.0-8.0 and in the presence of 2.0-3.0 % (w/v) NaCl. Neighbour-joining, maximum-likelihood and maximum-parsimony phylogenetic trees based on 16S rRNA gene sequences revealed that strain D1-W8(T) clustered with the type strain of Pelagicola litoralis showing 97.1 % sequence identity. 16S rRNA gene sequences of the type strains of other species exhibited lower similarity values. Strain D1-W8(T) was determined to contain Q-10 as the predominant ubiquinone and C18:1 ω7c as the predominant fatty acid. The major polar lipids of strain D1-W8(T) were identified as phosphatidylcholine, phosphatidylglycerol, phosphatidylethanolamine, one unidentified aminolipid and one unidentified lipid. The DNA G+C content of strain D1-W8(T) was determined to be 57.9 mol% and its DNA-DNA relatedness value with the type strain of P. litoralis was 17 %. The differential phenotypic properties, together with the phylogenetic and genetic distinctiveness, revealed that strain D1-W8(T) is separate from P. litoralis. On the basis of the data presented, strain D1-W8(T) is considered to represent a novel species of the genus Pelagicola, for which the name Pelagicola litorisediminis sp. nov. is proposed. The type strain is D1-W8(T) (= KCTC 32327(T) = CECT 8287(T)).

Glutathione enhances 2-keto-l-gulonic acid production based on Ketogulonicigenium vulgare model iWZ663.

Ketogulonicigenium vulgare is used widely during the industrial production of 2-keto-l-gulonic acid (2-KLG), the precursor of vitamin C, in a coculture with Bacillus megaterium. We analyzed the sulfate and coenzyme A metabolic module in the genome-scale metabolic model (GSMM) iWZ663 and found that the poor growth of K. vulgare was due to a deficiency in key reductases in the sulfate metabolic pathway. To carefully investigate the metabolism of sulfate, we developed a chemically defined medium (CDM) to produce pure cultures of K. vulgare. The addition of glutathione and l-cysteine to a flask culture of K. vulgare increased the cell growth, 2-KLG titer, and the intracellular coenzyme A level by 38.7%, 45.5%, and 85.3%, respectively, with glutathione, and by 25.6%, 35.8%, and 44.7%, respectively, with l-cysteine. The addition of glutathione to a 7-L fermenter culture of K. vulgare and B. megaterium increased the 2-KLG productivity by 20.9%. This study shows that the analysis of a specific metabolic module in GSMM can provide a potential strategy for optimizing microbial physiological functions.

Pannonibacter indica sp. nov., a highly arsenate-tolerant bacterium isolated from a hot spring in India.

A novel aerobic bacterium, strain HT23(T), able to grow on 500 mM sodium arsenate was isolated from a hot-spring sediment sample collected from Athamallik, Orissa, India. Cells of this isolate were Gram negative. Heterotrophic growth was observed at pH 6.0-11.0 and 20-45 °C. Optimum growth was observed at 37 °C and pH 7.0-10.0. The major polar lipids are diphosphatidyl glycerol, phosphatidyl glycerol, phosphatidyl ethanolamine, phosphatidyl choline and phosphatidyl monomethyl ethanolamine. The major isoprenoid quinone was Q-10. 16S rRNA gene sequence analysis indicated that the bacterium clustered with the genus Pannonibacter and showed 98.9 % similarity with Pannonibacter phragmitetus C6-19(T) (DSM 14782(T)) and 98 % with the P. phragmitetus group B and P. phragmitetus group E strains. Levels of DNA-DNA relatedness between the strain HT23(T) and P. phragmitetus C6-19(T) (DSM 14782(T)) and other strains of P. phragmitetus group B and group E strains were below 55 %. On the basis of phenotypic and chemotaxonomic characteristics, 16S rRNA gene sequence analysis and DNA-DNA hybridization data, strain HT23(T) is considered to represent a novel species of the genus Pannonibacter, for which the name Pannonibacter indica sp. nov. is proposed. The type strain is HT23(T) (=JCM 16851(T) = DSM 23407(T) = LMG 25769(T)).

Metabolomic analysis of the positive effects on Ketogulonigenium vulgare growth and 2-keto-L-gulonic acid production by reduced glutathione.

Ketogulonigenium vulgare has long been used in industry to produce 2-keto-L-gulonic acid (2KGA), the precursor of vitamin C. This fermentation process involves co-culture of K. vulgare and a Bacillus species. Early studies demonstrated that the presence of the Bacillus strain can enhance the cellular growth and 2KGA production of K. vulgare. However, the molecular mechanism behind how Bacillus affects the growth of K. vulgare and 2KGA production remains unclear. In addition, the inclusion of Bacillus in the fermentation process presents difficulties for the post-separation and purification of 2KGA. To address these issues, efforts have been made to replace the Bacillus strain with chemical compounds. In this study, we found that adding thiol compounds such as reduced glutathione (GSH) and dithiothreitol (DTT) to the K. vulgare mono-culture system can increase the growth of K. vulgare about twofold, and increase 2KGA production by about fivefold. The effects of thiols on the concentrations of some cellular metabolites were determined using gas chromatography coupled to time-of-flight mass spectrometry. The results showed that the levels of intracellular amino acids and intermediates in the pentose phosphate pathway increased significantly after thiol addition. Interestingly, when GSH was added, the levels of key intracellular metabolites in primary metabolic pathways and the cell biomass both reached their maximum in the first 36 h, and then decreased when the thiol was exhausted. These findings indicate that cell growth needs the assistance of a high concentration of thiols. This study is the first report that chemically defined compounds were used to enhance the growth of K. vulgare and 2KGA production. Furthermore, it also provides new insights into the possible cellular interaction between Bacillus species and K. vulgare.

Poly-ethers from Winogradskyella poriferorum: Antifouling potential, time-course study of production and natural abundance.

A sponge-associated bacterium, Winogradskyella poriferorum strain UST030701-295T was cultured up to 100l for extraction of antifouling bioactive compounds. Five poly-ethers were isolated and partially characterized based on nuclear magnetic resonance (NMR) spectroscopy and mass spectrometry (MS); two of them showed inhibitory effects on biofilm formation of marine bacteria and larval settlement of macro-foulers but did not produce any adverse effects on the phenotypes of zebra fish embryos at a concentration of 5µg ml(-1). The effect of culture duration on the production of the poly-ethers and the bioactivity of the relevant extracts was monitored over a period of 12 days. The total crude poly-ether production increased from day 2 to day 5 and the highest bioactivity was observed on day 3. The poly-ethers were found to be localized in the cellular fraction of the extracts, implying their natural occurrence. The potent bioactivity of these poly-ethers together with their high natural abundance in bacteria makes them promising candidates as ingredients in antifouling applications.