Thermoflavifilum aggregans gen. nov., sp. nov., a thermophilic and slightly halophilic filamentous bacterium from the phylum Bacteroidetes

Nematodes alter the taxonomic and functional profiles of benthic bacterial communities: A metatranscriptomic approach

Marine sediments cover 70% of the Earth's surface, and harbour diverse bacterial communities critical for marine biogeochemical processes, which affect climate change, biodiversity and ecosystem functioning. Nematodes, the most abundant and species-rich metazoan organisms in marine sediments, in turn, affect benthic bacterial communities and bacterial-mediated ecological processes, but the underlying mechanisms by which they affect biogeochemical cycles remain poorly understood. Here, we demonstrate using a metatranscriptomic approach that nematodes alter the taxonomic and functional profiles of benthic bacterial communities. We found particularly strong stimulation of nitrogen-fixing and methane-oxidizing bacteria in the presence of nematodes, as well as increased functional activity associated with methane metabolism and degradation of various carbon compounds. This study provides empirical evidence that the presence of nematodes results in taxonomic and functional shifts in active bacterial communities, indicating that nematodes may play an important role in benthic ecosystem processes.

Prokaryotic Life Associated with Coal-Fire Gas Vents Revealed by Metagenomics

The natural combustion of underground coal seams leads to the formation of gas, which contains molecular hydrogen and carbon monoxide. In places where hot coal gases are released to the surface, specific thermal ecosystems are formed. Here, 16S rRNA gene profiling and shotgun metagenome sequencing were employed to characterize the taxonomic diversity and genetic potential of prokaryotic communities of the near-surface ground layer near hot gas vents in an open quarry heated by a subsurface coal fire. The communities were dominated by only a few groups of spore-forming Firmicutes, namely the aerobic heterotroph Candidatus Carbobacillus altaicus, the aerobic chemolitoautotrophs Kyrpidia tusciae and Hydrogenibacillus schlegelii, and the anaerobic chemolithoautotroph Brockia lithotrophica. Genome analysis predicted that these species can obtain energy from the oxidation of hydrogen and/or carbon monoxide in coal gases. We assembled the first complete closed genome of a member of uncultured class-level division DTU015 in the phylum Firmicutes. This bacterium, 'Candidatus Fermentithermobacillus carboniphilus' Bu02, was predicted to be rod-shaped and capable of flagellar motility and sporulation. Genome analysis showed the absence of aerobic and anaerobic respiration and suggested chemoheterotrophic lifestyle with the ability to ferment peptides, amino acids, N-acetylglucosamine, and tricarboxylic acid cycle intermediates. Bu02 bacterium probably plays the role of a scavenger, performing the fermentation of organics formed by autotrophic Firmicutes supported by coal gases. A comparative genome analysis of the DTU015 division revealed that most of its members have a similar lifestyle.

DEAD Box Protein DhR1 Is a Global Regulator Involved in the Bacterial Fitness and Virulence of Riemerella anatipestifer

DEAD box proteins perform diverse cellular functions in bacteria. Our group previously reported that the transposon Tn4531 insertion in Riean_0395 (designated dhR1), which encodes a putative DEAD box helicase, attenuated the virulence of R. anatipestifer strain YZb1. Here, we show that, compared to the wild-type (WT) R. anatipestifer strain Yb2, the growth or survival of the ΔdhR1 mutant in tryptic soy broth (TSB) was significantly decreased in response to cold, pH, osmotic stress, ethanol, Triton X-100, and oxidative stress, and the dhR1 deletion significantly reduced biofilm formation and the adhesion capacity to Vero cells, whereas the growth of ΔdhR1 was less impaired in iron-limited TSB. Moreover, the virulence of ΔdhR1 in ducklings was attenuated by about 80-fold, compared to the WT. In addition, a transcriptome analysis showed that the dhR1 deletion in the strain Yb2 affected the expression of 58 upregulated genes and 98 downregulated genes that are responsible for various functions. Overall, our work reveals that the deletion of DhR1 results in a broad effect on the bacterial fitness, biofilm formation, iron utilization, and virulence of R. anatipestifer, which makes it a global regulator. IMPORTANCE R. anatipestifer infection has been a continued and serious problem in many duck farms, but little is known about the mechanism underlying the pathogenesis of R. anatipestifer and how R. anatipestifer adapts to the external environment and thereby persists in duck farms. The results of this study demonstrate that the DEAD box protein DhR1 is required for the tolerance of R. anatipestifer to cold, pH, and other stresses, and it is also necessary for biofilm formation, iron utilization, and virulence in ducklings, demonstrating multiple functions of DhR1.

Biochemical characterization of the first step in sulfonolipid biosynthesis in Alistipes finegoldii

Sulfonolipids are unusual lipids found in the outer membranes of Gram-negative bacteria in the phylum Bacteroidetes. Sulfonolipid and its deacylated derivative, capnine, are sulfur analogs of ceramide-1-phosphate and sphingosine-1-phosphate, respectively; thus, sulfonolipid biosynthesis is postulated to be similar to the sphingolipid biosynthetic pathway. Here, we identify the first enzyme in sulfonolipid synthesis in Alistipes finegoldii as the product of the alfi_1224 gene, cysteate acyl-acyl carrier protein (ACP) transferase (SulA). We show SulA catalyzes the condensation of acyl-ACP and cysteate (3-sulfo-alanine) to form 3-ketocapnine. Acyl-CoA is a poor substrate. We show SulA has a bound pyridoxal phosphate (PLP) cofactor that undergoes a spectral redshift in the presence of cysteate, consistent with the transition of the lysine-aldimine complex to a substrate-aldimine complex. Furthermore, the SulA crystal structure shows the same prototypical fold found in bacterial serine palmitoyltransferases (Spts), enveloping the PLP cofactor bound to Lys251. We observed the SulA and Spt active sites are identical except for Lys281 in SulA, which is an alanine in Spt. Additionally, SulA(K281A) is catalytically inactive but binds cysteate and forms the external aldimine normally, highlighting the structural role of the Lys281 side chain in walling off the active site from bulk solvent. Finally, the electropositive groove on the protein surface adjacent to the active site entrance provides a landing pad for the electronegative acyl-ACP surface. Taken together, these data identify the substrates, products, and mechanism of SulA, the PLP-dependent condensing enzyme that catalyzes the first step in sulfonolipid synthesis in a gut commensal bacterium.

Thermophilic Chloroflexi Dominate in the Microbial Community Associated with Coal-Fire Gas Vents in the Kuznetsk Coal Basin, Russia

Thermal ecosystems associated with areas of underground burning coal seams are rare and poorly understood in comparison with geothermal objects. We studied the microbial communities associated with gas vents from the coal-fire in the mining wastes in the Kemerovo region of the Russian Federation. The temperature of the ground heated by the hot coal gases and steam coming out to the surface was 58 °C. Analysis of the composition of microbial communities revealed the dominance of Ktedonobacteria (the phylum Chloroflexi), known to be capable of oxidizing hydrogen and carbon monoxide. Thermophilic hydrogenotrophic Firmicutes constituted a minor part of the community. Among the well-known thermophiles, members of the phyla Aquificae, Deinococcus-Thermus and Bacteroidetes were also found. In the upper ground layer, Acidobacteria, Verrucomicrobia, Actinobacteria, Planctomycetes, as well as Proteobacteria of the alpha and gamma classes, typical of soils, were detected; their relative abundancies decreased with depth. The phylum Verrucomicrobia was dominated by Candidatus Udaeobacter, aerobic heterotrophs capable of generating energy through the oxidation of hydrogen present in the atmosphere in trace amounts. Archaea made up a small part of the communities and were represented by thermophilic ammonium-oxidizers. Overall, the community was dominated by bacteria, whose cultivated relatives are able to obtain energy through the oxidation of the main components of coal gases, hydrogen and carbon monoxide, under aerobic conditions.

Isolation, characterisation and genome analysis of a novel ginsenosides hydrolysing bacterium Ginsengibacter hankyongi gen. nov., sp. nov. isolated from soil

A novel yellow-pigmented bacterial strain (designated BR5-29^T), was isolated and its taxonomy was studied. Phylogenetic study based on the 16S rRNA and draft genome sequence placed the strain BR5-29^T in a distinct lineage within the family Chitinophagaceae, sharing ≤ 93.4% sequence similarity with members of the closely related genera Ferruginibacter, Flavisolibacter, Flavitalea and Niastella. The novel isolate showed the highest sequence similarity to the genus Ferruginibacter. The draft genome of strain BR5-29^T had a total length of 5,505,520 base pairs. A total of 4585 genes were identified, in which 4537 were CDS and 48 RNA genes were assigned a putative function. The genome annotation of BR5-29^T showed 225 carbohydrate genes which may be responsible for the conversion of major ginsenosides to minor ginsenosides. Strain BR5-29^T contained MK-7 as a predominant quinone, and iso-C_15:0, iso-C_15:0 G, iso-C_17:0 3-OH, and C_16:1 ω7c and/or C_16:1 ω6c (summed feature 3) as major fatty acids. The polar lipids found in the strain BR5-29^T were phosphatidylglycerol (PG), diphosphatidylglycerol (DPG), phosphatidylethanolamine (PE), five unidentified polar lipids (L1-L5), two unidentified aminolipid and one unidentified aminophospholipid. Our pilot data demonstrate that the novel isolate shares the similar major polar lipid PE, major quinone MK-7 and major fatty acids with the described members of the family Chitinophagaceae. However, the low 16S rRNA gene sequence (< 93.4%), the little high amount of C_12:0, iso-C_17:0 2-OH and iso-C_15:1 2-OH fatty acids, low DNA G + C content, and the presence of DPG, PG and two unidentified polar lipids (L1 and L3 differentiate the BR5-29^T from its closest phylogenetic neighbors. Thus, the isolate represents a novel genus and species in the family Chitinophagaceae for which the name Ginsengibacter hankyongi gen. nov., sp. nov. is proposed. The type strain is BR5-29^T (= KACC 19446^T = LMG 30462^T). Thus, we predict that this novel strain may prove useful for the future research analysis (target gene cloning) and mass production of Rg3.

Phototrophic Co-cultures From Extreme Environments: Community Structure and Potential Value for Fundamental and Applied Research

Cyanobacteria are found in most illuminated environments and are key players in global carbon and nitrogen cycling. Although significant efforts have been made to advance our understanding of this important phylum, still little is known about how members of the cyanobacteria affect and respond to changes in complex biological systems. This lack of knowledge is in part due to our dependence on pure cultures when determining the metabolism and function of a microorganism. We took advantage of the Culture Collection of Microorganisms from Extreme Environments (CCMEE), a collection of more than 1,000 publicly available photosynthetic co-cultures maintained at the Pacific Northwest National Laboratory, and assessed via 16S rRNA amplicon sequencing if samples readily available from public culture collection could be used in the future to generate new insights into the role of microbial communities in global and local carbon and nitrogen cycling. Results from this work support the existing notion that culture depositories in general hold the potential to advance fundamental and applied research. Although it remains to be seen if co-cultures can be used at large scale to infer roles of individual organisms, samples that are publicly available from existing co-cultures depositories, such as the CCMEE, might be an economical starting point for such studies. Access to archived biological samples, without the need for costly field work, might in some circumstances be one of the few remaining ways to advance the field and to generate new insights into the biology of ecosystems that are not easily accessible. The current COVID-19 pandemic, which makes sampling expeditions almost impossible without putting the health of the participating scientists on the line, is a very timely example.

Analysis of 1,000 Type-Strain Genomes Improves Taxonomic Classification of Bacteroidetes

Although considerable progress has been made in recent years regarding the classification of bacteria assigned to the phylum Bacteroidetes, there remains a need to further clarify taxonomic relationships within a diverse assemblage that includes organisms of clinical, piscicultural, and ecological importance. Bacteroidetes classification has proved to be difficult, not least when taxonomic decisions rested heavily on interpretation of poorly resolved 16S rRNA gene trees and a limited number of phenotypic features. Here, draft genome sequences of a greatly enlarged collection of genomes of more than 1,000 Bacteroidetes and outgroup type strains were used to infer phylogenetic trees from genome-scale data using the principles drawn from phylogenetic systematics. The majority of taxa were found to be monophyletic but several orders, families and genera, including taxa proposed long ago such as Bacteroides, Cytophaga, and Flavobacterium but also quite recent taxa, as well as a few species were shown to be in need of revision. According proposals are made for the recognition of new orders, families and genera, as well as the transfer of a variety of species to other genera. In addition, emended descriptions are given for many species mainly involving information on DNA G+C content and (approximate) genome size, both of which can be considered valuable taxonomic markers. We detected many incongruities when comparing the results of the present study with existing classifications, which appear to be caused by insufficiently resolved 16S rRNA gene trees or incomplete taxon sampling. The few significant incongruities found between 16S rRNA gene and whole genome trees underline the pitfalls inherent in phylogenies based upon single gene sequences and the impediment in using ordinary bootstrapping in phylogenomic studies, particularly when combined with too narrow gene selections. While a significant degree of phylogenetic conservation was detected in all phenotypic characters investigated, the overall fit to the tree varied considerably, which is one of the probable causes of misclassifications in the past, much like the use of plesiomorphic character states as diagnostic features.

Thermophilic methanotrophs: in hot pursuit

Methane is a potent greenhouse gas responsible for 20–30% of global climate change effects. The global methane budget is ∼500–600 Tg y−1, with the majority of methane produced via microbial processes, including anthropogenic-mediated sources such as ruminant animals, rice fields, sewage treatment facilities and landfills. It is estimated that microbially mediated methane oxidation (methanotrophy) consumes >50% of global methane flux each year. Methanotrophy research has primarily focused on mesophilic methanotrophic representatives and cooler environments such as freshwater, wetlands or marine habitats from which they are sourced. Nevertheless, geothermal emissions of geological methane, produced from magma and lithosphere degassing micro-seepages, mud volcanoes and other geological sources, contribute an estimated 33–75 Tg y−1 to the global methane budget. The aim of this review is to summarise current literature pertaining to the activity of thermophilic and thermotolerant methanotrophs, both proteobacterial (Methylocaldum, Methylococcus, Methylothermus) and verrucomicrobial (Methylacidiphilum). We assert, on the basis of recently reported molecular and geochemical data, that geothermal ecosystems host hitherto unidentified species capable of methane oxidation at higher temperatures.

Edaphocola aurantiacus gen. nov., sp. nov., a new member of the family Chitinophagaceae isolated from wetland soil in South Korea

A short rod-shaped, yellow-orange pigmented, strictly aerobic bacterium, designated as strain H2^T, was isolated from the wetland soil of Halla Mountain, Jeju-island, South Korea. Growth was observed at temperatures of 10-30 °C (optimum at 25-30 °C), pH of 6-8 (optimum at pH 7), and salt concentrations of 0-1% (w/v) NaCl (optimum at 0%). The strain H2^T was found to be a catalase and oxidase-positive, non-motile, Gram-negative bacterium. On the basis of 16S rRNA gene sequence similarity and phylogenetic analysis, strain H2^T was found to be related to the members of the Chitinophagaceae family, being closely related to Taibaiella chishuiensis AY17^T (94.3% sequence similarity). The major polar lipids are phosphatidylethanolamine and glycolipid. Strain H2^T contained MK-7 as the only menaquinone as well as iso-C_15:0, iso-C_15:1 G and iso-C_17:0 3-OH as the major fatty acids (> 15%). The DNA G+C content of strain H2^T was determined to be 48.3 mol%. Based on the phylogenetic, phenotypic characteristics and chemotaxonomic analysis data, strain H2^T (= KCTC 62115^T = JCM 32353^T) should be classified as representative of a novel species of a novel genus within the family Chitinophagaceae, for which the name Edaphocola aurantiacus gen. nov., sp. nov., is proposed.

Edaphobaculum flavum gen. nov., sp. nov., a member of family Chitinophagaceae, isolated from grassland soil

A yellow-coloured, Gram-stain-negative, non-motile, rod-shaped, strictly aerobic bacterium, designated 1-116^T, was isolated from Erdos grassland soil of Inner Mongolia, PR China. Phylogenetic analysis based on 16S rRNA genes showed that strain 1-116^T was a member of family Chitinophagaceae and exhibited the highest similarities to Taibaiella koreensis THG-DT86^T (90.1 %) and Flavihumibacter solisivae 3-3^T (90.0 %), while the similarities to the other Chitinophagaceae type strains were lower than 90.0 %. Strain 1-116^T grew at 16-33 °C (optimum 28 °C), pH 6.0-9.0 (optimum 7.0-8.0) and 0-0.5 % NaCl (w/v; optimum without NaCl). A flexirubin-type pigment was present. The DNA G+C content was 43.2 mol% and the only quinone present was menaquinone-7. The only polyamine detected was sym-homospermidine [30.7 µmol (g dry weight)^-1] and the predominant fatty acids were iso-C15 : 0 (20.8 %), iso-C15 : 1 G (25.1 %), summed feature 4 (anteiso-C17 : 1 B and/or iso-C17 : 1 I; 13.8 %) and iso-C17 : 0 3-OH (13.2 %). The major polar lipids were phosphatidylethanolamine, three unidentified lipids, an unidentified aminophospholipid and an unidentified glycolipid. On the basis of the polyphasic analyses, strain 1-116^T represents a novel genus and species in the family Chitinophagaceae, for which the name Edaphobaculum flavum gen. nov., sp. nov., is proposed. The type strain of Edaphobaculum flavum is 1-116^T (=CCTCC AB 2017054=KCTC 52843).

Heat Stress Dictates Microbial Lipid Composition along a Thermal Gradient in Marine Sediments

Temperature exerts a first-order control on microbial populations, which constantly adjust the fluidity and permeability of their cell membrane lipids to minimize loss of energy by ion diffusion across the membrane. Analytical advances in liquid chromatography coupled to mass spectrometry have allowed the detection of a stunning diversity of bacterial and archaeal lipids in extreme environments such as hot springs, hydrothermal vents and deep subsurface marine sediments. Here, we investigated a thermal gradient from 18 to 101°C across a marine sediment field and tested the hypothesis that cell membrane lipids provide a major biochemical basis for the bioenergetics of archaea and bacteria under heat stress. This paper features a detailed lipidomics approach with the focus on membrane lipid structure-function. Membrane lipids analyzed here include polar lipids of bacteria and polar and core lipids of archaea. Reflecting the low permeability of their ether-linked isoprenoids, we found that archaeal polar lipids generally dominate over bacterial lipids in deep layers of the sediments influenced by hydrothermal fluids. A close examination of archaeal and bacterial lipids revealed a membrane quandary: not only low permeability, but also increased fluidity of membranes are required as a unified property of microbial membranes for energy conservation under heat stress. For instance, bacterial fatty acids were composed of longer chain lengths in concert with higher degree of unsaturation while archaea modified their tetraethers by incorporation of additional methyl groups at elevated sediment temperatures. It is possible that these configurations toward a more fluidized membrane at elevated temperatures are counterbalanced by the high abundance of archaeal glycolipids and bacterial sphingolipids, which could reduce membrane permeability through strong intermolecular hydrogen bonding. Our results provide a new angle for interpreting membrane lipid structure-function enabling archaea and bacteria to survive and grow in hydrothermal systems.

Compostibacter hankyongensis gen. nov., &nbsp;sp. nov., isolated from compost

A novel bacterial strain, designated strain BS27T, was isolated from mushroom compost and subjected to a taxonomic study using a polyphasic approach. Colonies of BS27T were milky-white, circular with regular fringes and opaque. Cells were short rods, 0.3-0.5 µm wide and 1.2-2.0 µm long. Phylogenetic study based on the 16S rRNA gene sequence placed BS27T in a distinct lineage in the family Chitinophagaceae, sharing 90.1-90.9 % sequence similarity with members of the closely related genera Chitinophaga, Flavitalea, Flavihumibacter, Lacibacter and Flavisolibacter. The novel isolate showed the highest sequence similarities with the members of the genus Chitinophaga. BS27T contained MK-7 as predominant quinone, and iso-C15 : 0, iso-C17 : 0 3-OH, C16 : 1ω7c and/or C16 : 1ω6c (summed feature 3) and iso-C17 : 1I and/or anteiso-C17 : 1B (summed feature 4) as major fatty acids. The DNA G+C content was 53.0 mol%. The major polar lipids of BS27T were phosphatidylethanolamine (PE) and five unidentified polar lipids (L1, L2, L5, L6 and L7). The results of physiological and biochemical tests allowed phenotypic differentiation of BS27T from its closest phylogenetic neighbours. On the basis of the evidence of this polyphasic study, isolate BS27T represents a novel genus and species in the family Chitinophagaceae for which the name Compostibacter hankyongensisgen. nov., sp. nov. is proposed. The type strain is BS27T (=KACC 18745T=JCM 17664T).

Hydrobacter penzbergensis gen. nov., sp. nov., isolated from purified water

A Gram-negative, oxidase- and catalase-positive bacterium, designated strain EM 4(T), which varied in shape from rod-shaped to curved or helical with frequently observed bulb-shaped protuberances, was isolated from purified water. 16S rRNA gene sequence analysis indicated that the novel strain belongs to the family Chitinophagaceae within the phylum Bacteroidetes; the closest relative among bacterial species with validly published names was determined to be Sediminibacterium salmoneum NBRC 103935(T), with 93.4 % sequence identity. The main fatty acids of strain EM 4(T) were iso-C15 : 0, iso-C15 : 1 and iso-C17 : 0 3-OH. The polar lipid profile consisted of phosphatidylethanolamine, aminolipids, aminophospholipids and unknown lipids; the quinone system consisted of menaquinone MK-7. 16S rRNA gene sequence analysis and the polar lipid and fatty acid profiles suggest that the strain represents a novel genus and species, for which the name Hydrobacter penzbergensis gen. nov., sp. nov. is proposed. The type strain of Hydrobacter penzbergensis is strain EM 4(T) ( = DSM 25353(T) = CCUG 62278(T)).