Unveiling the regulatory mechanisms of salicylate degradation gene cluster cehGHIR4 in Rhizobium sp. strain X9

In a previous study, the novel gene cluster cehGHI was found to be involved in salicylate degradation through the CoA-mediated pathway in Rhizobium sp. strain X9 (Mol Microbiol 116:783-793, 2021). In this study, an IclR family transcriptional regulator CehR4 was identified. In contrast to other regulators involved in salicylate degradation, cehR4 forms one operon with the gentisyl-CoA thioesterase gene cehI, while cehG and cehH (encoding salicylyl-CoA ligase and salicylyl-CoA hydroxylase, respectively) form another operon. cehGH and cehIR4 are divergently transcribed, and their promoters overlap. The results of the electrophoretic mobility shift assay and DNase I footprinting showed that CehR4 binds to the 42-bp motif between genes cehH and cehI, thus regulating transcription of cehGH and cehIR4. The repeat sequences IR1 (5'-TTTATATAAA-3') and IR2 (5'-AATATAGAAA-3') in the motif are key sites for CehR4 binding. The arrangement of cehGH and cehIR4 and the conserved binding motif of CehR4 were also found in other bacterial genera. The results disclose the regulatory mechanism of salicylate degradation through the CoA pathway and expand knowledge about the systems controlled by IclR family transcriptional regulators.IMPORTANCEThe long-term residue of aromatic compounds in the environment has brought great threat to the environment and human health. Microbial degradation plays an important role in the elimination of aromatic compounds in the environment. Salicylate is a common intermediate metabolite in the degradation of various aromatic compounds. Recently, Rhizobium sp. strain X9, capable of degrading the pesticide carbaryl, was isolated from carbaryl-contaminated soil. Salicylate is the intermediate metabolite that appeared during the degradation of carbaryl, and a novel salicylate degradation pathway and the involved gene cluster cehGHIR4 have been identified. This study identified and characterized the IclR transcription regulator CehR4 that represses transcription of cehGHIR4 gene cluster. Additionally, the genetic arrangements of cehGH and cehIR4 and the binding sites of CehR4 were also found in other bacterial genera. This study provides insights into the biodegradation of salicylate and provides an application in the bioremediation of aromatic compound-contaminated environments.

Parasedimentitalea psychrophila sp. nov., a psychrophilic bacterium isolated from deep-sea sediment

A novel bacterium, strain QS115T, was isolated from deep-sea sediment collected from the South China Sea at a depth of 1151 m. Phylogenetic analyses based on 16S rRNA gene sequences indicated that QS115T was most closely related to Parasedimentitalea marina W43T, with similarity of 98.21 %. Strain QS115T shared 82.39 % average nucleotide identity, 26.3 % digital DNA-DNA hybridization and 85.32 % average amino acid identity with P. marina W43T. Cells of strain QS115T were Gram-stain-negative, rod-shaped and grew optimally at 10 °C, pH 7.5 and 2 % (w/v) NaCl. The principal fatty acids were summed feature 8 (C18 : 1  ω7c/ω6c), the major respiratory quinone was ubiquinone-10 and predominant polar lipids were diphosphatidylglycerol, phosphatidylethanolamine, glycophospholipid, phosphatidylglycerol and phosphatidylcholine. Polyphasic analyses of physiological and phenotypic characteristics and genomic studies suggested that strain QS115T represents a novel species of the genus Parasedimentitalea, for which the name Parasedimentitalea psychrophila sp. nov. is proposed (type strain QS115T=MCCC 1K04395T=JCM 34219T).

Marine Fungi Select and Transport Aerobic and Anaerobic Bacterial Populations from Polycyclic Aromatic Hydrocarbon-Contaminated Sediments

The organization of microbial communities in marine sediment relies on complex biotic and abiotic interactions. Among them, the interaction between fungi and bacteria plays a crucial role building specific microbial assemblages, resulting in metabolic networks adapted to environmental conditions. The fungal-bacterial interaction (FBI) includes bacterial translocation via fungal mycelia, allowing bacterial dispersion, and ecological niche colonization. In order to demonstrate that the translocation of bacteria through fungal mycelia involves bacterial selection, the mycelia of two fungi isolated from marine coastal sediment, Alternaria destruens F10.81 and Fusarium pseudonygamai F5.76, showing different strategies for uptake of polycyclic aromatic hydrocarbon (PAH), homogenous internalization and vacuole forming respectively, were used to translocate bacteria through hydrophobic hydrocarbon contaminated sediments. A. destruens F10.81 selected four specific bacteria, while bacterial selection by F. pseudonygamai F5.76 was not evident. Among the bacteria selected by A. destruens F10.81, Spirochaeta litoralis, known as strictly anaerobic bacterium, was identified, indicating that A. destruens F10.81 selects and transports both aerobic and anaerobic bacteria. Such a result is consistent with the observed formation of anoxic micro-niches in areas surrounding and affected by fungal hyphae. Our findings provide new insights on the selection and dispersion of bacterial communities by fungi, which are crucial for the organization of microbial communities and their functioning in coastal PAH-contaminated sediments. IMPORTANCE The study provides advances for understanding fungal-bacterial relationships, particularly on the selection and dispersion of bacterial communities by fungi, which are crucial for the organization of microbial communities and their functioning in coastal PAH-contaminated sediments. The transportation of bacteria via fungal hyphae (fungal highway) results in bacterial selection; in particular, fungal hyphae offer adequate conditions for the transport of both aerobic and anaerobic bacteria through hydrophobic patches for the colonization of novel niches.

Sinomicrobium weinanense sp. nov., a halophilic bacterium isolated from saline-alkali soil

A Gram-stain-negative, facultative anaerobic, non-motile, rod-shaped strain was isolated from saline-alkali soil collected in PR China, and it was designated as strain FJxs T . Its optimal growth was observed at 37–40 °C in the presence of 0–3 % (w/v) NaCl (pH 7.0). The major fatty acids of strain FJxs T were iso-C15 : 0, iso-C17 : 0 3OH, summed feature 3, C16 : 0 and iso-C15 : 1 G. The predominant respiratory quinone was menaquinone 6. The DNA G+C content of the strain was 45.18 mol%. Whole genome and 16S rRNA gene sequence analyses indicated that strain FJxs T exhibited 94.78 % sequence identity (the maximum) with Sinomicrobium soli N-1-3-6T, 94.36 % with Sinomicrobium pectinilyticum 5DNS001T, and 93.52 % with Sinomicrobium oceani SCSIO 03483T. Analyses of genotypic, phenotypic, phylogenetic and chemotaxonomic characteristics indicated that strain FJxs T represented a novel species of the genus Sinomicrobium . This novel species was named Sinomicrobium weinanense sp. nov. with its type strain as FJxs T (=CCTCC AB 2019251T=KCTC 72740T).

Genome Analysis of Celeribacter sp. PS-C1 Isolated from Sekinchan Beach in Selangor, Malaysia, Reveals Its β-Glucosidase and Licheninase Activities

A halophilic marine bacterial strain, PS-C1, was isolated from Sekinchan beach in Selangor, Malaysia. The 16S rRNA gene sequence analysis indicated that strain PS-C1 was associated with the genus Celeribacter. To date, there have been no reports on enzymes from the genus Celeribacter. The present study reports on the cellular features of Celeribacter sp. PS-C1, its annotated genome sequence, and comparative genome analyses of Celeribacter glycoside hydrolase (GH) enzymes. The genome of strain PS-C1 has a size of 3.87 Mbp and a G+C content of 59.10%, and contains 3739 protein-coding genes. Detailed analysis using the Carbohydrate-Active enZYmes (CAZy) database revealed that Celeribacter genomes harboured at least 12 putative genes encoding industrially important GHs that are grouped as cellulases, β-glucanases, hemicellulases, and starch-degrading enzymes. Herein, the potential applications of these enzymes are discussed. Furthermore, the activities of two types of GHs (β-glucosidase and licheninase) in strain PS-C1 were demonstrated. These findings suggest that strain PS-C1 could be a reservoir of novel GH enzymes for lignocellulosic biomass degradation.

Celeribacter litoreus sp. nov., isolated from intertidal sediment

A Gram-negative, aerobic, non-flagellated and rod-shaped bacterium, strain ASW11-22^T, was isolated from an intertidal sediment collected from a coastal area of Qingdao, PR China. The strain grew at 15-40 °C (optimum, 37 °C), at pH 6.0-9.0 (optimum, pH 7.0) and with 0.5-10 % (w/v) NaCl (optimum, 1.0 %). It hydrolysed gelatin and aesculin but did not reduce nitrate to nitrite. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain ASW11-22^T belonged to the genus Celeribacter, showing the highest sequence similarity to the type strains of Celeribacter halophilus MCCC 1A06432^T (98.20 %) and Celeribacter ethanolicus NH195^T (97.84 %). The genomic DNA G+C content was 59.1 mol%. The major cellular fatty acid (>10 %) of the strain was summed feature 8 (C_18 : 1 ω7c and/or C_18 : 1 ω6c) and its main polar lipids were phosphatidylglycerol and one unidentified aminolipid. The sole respiratory quinone of strain ASW11-22^T was ubiquinone-10. On the basis of the polyphasic evidence presented in this paper, strain ASW11-22^T represents a novel Celeribacter species, for which the name Celeribacter litoreus sp. nov. is proposed. The type strain is ASW11-22^T (=KCTC 82495^T=MCCC 1K05584^T).

Biotechnological applications of marine bacteria in bioremediation of environments polluted with hydrocarbons and plastics

Marine ecosystems are some of the most adverse environments on Earth and contain a considerable portion of the global bacterial population, and some of these bacterial species play pivotal roles in several biogeochemical cycles. Marine bacteria have developed different molecular mechanisms to address fluctuating environmental conditions, such as changes in nutrient availability, salinity, temperature, pH, and pressure, making them attractive for use in diverse biotechnology applications. Although more than 99% of marine bacteria cannot be cultivated with traditional microbiological techniques, several species have been successfully isolated and grown in the laboratory, facilitating investigations of their biotechnological potential. Some of these applications may contribute to addressing some current global problems, such as environmental contamination by hydrocarbons and synthetic plastics. In this review, we first summarize and analyze recently published information about marine bacterial diversity. Then, we discuss new literature regarding the isolation and characterization of marine bacterial strains able to degrade hydrocarbons and petroleum-based plastics, and species able to produce biosurfactants. We also describe some current limitations for the implementation of these biotechnological tools, but also we suggest some strategies that may contribute to overcoming them. KEY POINTS: • Marine bacteria have a great metabolic capacity to degrade hydrocarbons in harsh conditions. • Marine environments are an important source of new bacterial plastic-degrading enzymes. • Secondary metabolites from marine bacteria have diverse potential applications in biotechnology.

Mle046 Is a Marine Mesophilic MHETase-Like Enzyme

Accumulation of plastics in the oceans presents a major threat to diverse ecosystems. The introduction of biodegradable plastics into the market aims to alleviate the ecological burden caused by recalcitrant plastics. Poly (butylene adipate-co-terephthalate) (PBAT) is a biodegradable commercial plastic that can be biodegraded similarly to polyethylene terephthalate (PET) by PETase-like enzymes and MHETases. The role of MHETases is to hydrolyze the intermediate degradation product of PET, mono-2-hydroxyethyl terephthalate (MHET) to its monomers. We recently identified a homolog of the MHETase of the PET-degrading bacterium Ideonella sakaiensis, Mle046, from a marine microbial consortium. In this consortium, Mle046 was highly expressed when a PBAT-based blend film (PF) was supplied as the sole carbon source. In this study, we recombinantly expressed and biochemically characterized Mle046 under different conditions. Mle046 degrades MHET but also 4-(4-hydroxybutoxycarbonyl) benzoic acid (Bte), the intermediate of PF degradation. Mle046 is a mesophilic enzyme adapted to marine conditions, which rapidly degrades MHET to terephthalate and ethylene glycol at temperatures between 20 and 40°C. Mle046 degradation rates were similar for Bte and MHET. Despite its mesophilic tendency, Mle046 retains a considerable amount of activity at temperatures ranging from 10 to 60°C. In addition, Mle046 is active at a range of pH values from 6.5 to 9. These characteristics make Mle046 a promising candidate for biotechnological applications related to plastic recycling.

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 WDS1C4^T and WDS4C29^T, were isolated from a marine solar saltern in Weihai, Shandong Province, PR China. Growth of strain WDS1C4^T 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 WDS4C29^T 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 WDS1C4^T and WDS4C29^T were phosphatidylglycerol, phosphatidylethanolamine and phosphatidylcholine. The major cellular fatty acid in strains WDS1C4^T and WDS4C29^T was C_18 : 1  ω7c, and the genomic DNA G+C contents of strains WDS1C4^T and WDS4C29^T were 67.6 and 63.3 mol%, respectively. Phylogenetic analyses based on 16S rRNA gene sequences indicated that strains WDS1C4^T and WDS4C29^T were members of the family Rhodobacteraceae and showed 94.3 and 95.3 % similarities to their closest relative, Celeribacter indicus, respectively. The similarity between WDS1C4^T and WDS4C29^T 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 WDS1C4^T=MCCC 1H00179^T=KCTC 52542^T) and Salibaculum griseiflavum sp. nov. (WDS4C29^T=MCCC 1H00175^T=KCTC 52541^T) are proposed.

The role of gut microbial community and metabolomic shifts in adaptive resistance of Atlantic killifish (Fundulus heteroclitus) to polycyclic aromatic hydrocarbons

Altered gut microbiomes may play a role in rapid evolution to anthropogenic change but remain poorly understood. Atlantic killifish (Fundulus heteroclitus) in the Elizabeth River, VA have evolved resistance to polycyclic aromatic hydrocarbons (PAHs) and provide a unique opportunity to examine the links between shifts in the commensal microbiome and organismal physiology associated with evolved resistance. Here, 16S rRNA sequence libraries derived from fish guts and sediments sampled from a highly PAH contaminated site revealed significant differences collected at similar samples from an uncontaminated site. Phylogenetic groups enriched in the libraries derived from PAH-resistant fish were dissimilar to their associated sediment libraries, suggesting the specific environment within the PAH-resistant fish intestine influence the gut microbiome composition. Gut metabolite analysis revealed shifts between PAH-resistant and non-resistant subpopulations. Notably, PAH-resistant fish exhibited reduced levels of tryptophan and increased levels of sphingolipids. Exposure to PAHs appears to impact several bacterial in the gut microbiome, particularly sphingolipid containing bacteria. Bacterial phylotypes known to include species containing sphingolipids were generally lower in the intestines of fish subpopulations exposed to high concentrations of PAHs, inferring a complex host-microbiome relationship. Overall, killifish microbial community shifts appear to be related to a suppression of overall metabolite level, indicating a potential role of the gut in organismal response to anthropogenic environmental change. These results on microbial and metabolomics shifts are potentially linked to altered bioenergetic phenotype observed in the same PAH-resistant killifish populations in other studies.

Unveiling the CoA mediated salicylate catabolic mechanism in Rhizobium sp. X9

Salicylate is a typical aromatic compound widely distributed in nature. Microbial degradation of salicylate has been well studied and salicylate hydroxylases play essential roles in linking the peripheral and ring-cleavage catabolic pathways. The direct hydroxylation of salicylate catalyzed by salicylate-1-hydroxylase or salicylate-5-hydroxylase has been well studied. However, the CoA mediated salicylate 5-hydroxylation pathway has not been characterized in detail. Here, we elucidate the molecular mechanism of the reaction in the conversion of salicylate to gentisate in the carbaryl-degrading strain Rhizobium sp. X9. Three enzymes (salicylyl-CoA ligase CehG, salicylyl-CoA hydroxylase CehH and gentisyl-CoA thioesterase CehI) catalyzed the conversion of salicylate to gentisate via a route, including CoA thioester formation, hydroxylation and thioester hydrolysis. Further analysis indicated that genes cehGHI are also distributed in other bacteria from terrestrial environment and marine sediments. These genomic evidences highlight the role of this salicylate degradation pathway in the carbon cycle of soil organic compounds and marine sediments. Our findings of this three-step strategy enhanced the current understanding of CoA mediated degradation of salicylate.

First Report on the Plasmidome From a High-Altitude Lake of the Andean Puna

Mobile genetic elements, including plasmids, drive the evolution of prokaryotic genomes through the horizontal transfer of genes allowing genetic exchange between bacteria. Moreover, plasmids carry accessory genes, which encode functions that may offer an advantage to the host. Thus, it is expected that in a certain ecological niche, plasmids are enriched in accessory functions, which are important for their hosts to proliferate in that niche. Puquio de Campo Naranja is a high-altitude lake from the Andean Puna exposed to multiple extreme conditions, including high UV radiation, alkalinity, high concentrations of arsenic, heavy metals, dissolved salts, high thermal amplitude and low O₂ pressure. Microorganisms living in this lake need to develop efficient mechanisms and strategies to cope under these conditions. The aim of this study was to characterize the plasmidome of microbialites from Puquio de Campo Naranja, and identify potential hosts and encoded functions using a deep-sequencing approach. The potential ecological impact of the plasmidome, including plasmids from cultivable and non-cultivable microorganisms, is described for the first time in a lake representing an extreme environment of the Puna. This study showed that the recovered genetic information for the plasmidome was novel in comparison to the metagenome derived from the same environment. The study of the total plasmid population allowed the identification of genetic features typically encoded by plasmids, such as resistance and virulence factors. The resistance genes comprised resistances to heavy metals, antibiotics and stress factors. These results highlight the key role of plasmids for their hosts and impact of extrachromosomal elements to thrive in a certain ecological niche.

Analysis of 1,000+ Type-Strain Genomes Substantially Improves Taxonomic Classification of Alphaproteobacteria

The class Alphaproteobacteria is comprised of a diverse assemblage of Gram-negative bacteria that includes organisms of varying morphologies, physiologies and habitat preferences many of which are of clinical and ecological importance. Alphaproteobacteria classification has proved to be difficult, not least when taxonomic decisions rested heavily on a limited number of phenotypic features and interpretation of poorly resolved 16S rRNA gene trees. Despite progress in recent years regarding the classification of bacteria assigned to the class, there remains a need to further clarify taxonomic relationships. Here, draft genome sequences of a collection of genomes of more than 1000 Alphaproteobacteria 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 recognized as problematic long ago 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 and of a variety of genera to other families. In addition, emended descriptions are given for many species mainly involving information on DNA G+C content and (approximate) genome size, both of which are confirmed as valuable taxonomic markers. Similarly, analysis of the gene content was shown to provide valuable taxonomic insights in the class. Significant incongruities between 16S rRNA gene and whole genome trees were not found in the class. The incongruities that became obvious when comparing the results of the present study with existing classifications appeared to be caused mainly by insufficiently resolved 16S rRNA gene trees or incomplete taxon sampling. Another probable cause of misclassifications in the past is the partially low overall fit of phenotypic characters to the sequence-based tree. Even though a significant degree of phylogenetic conservation was detected in all characters investigated, the overall fit to the tree varied considerably.

Georhizobium profundi gen. nov., sp. nov., a piezotolerant bacterium isolated from a deep-sea sediment sample of the New Britain Trench

A novel alphaproteobacterium, strain WS11T, was isolated from a deep-sea sediment sample collected from the New Britain Trench. The full-length 16S rRNA gene of strain WS11T had the highest sequence similarity of 97.6 % to Rhizobium subbaraonis JC85T, followed by Mycoplana ramosa DSM 7292T (96.9 %) and Rhizobium azooxidifex Po 20/26T (96.8 %). Phylogenetic analysis of concatenated 16S rRNA, atpD and recA gene sequences showed that strain WS11T was deeply separated from the species within the family Rhizobiaceae. Phylogenomic analysis based on the whole-genome protein sequences showed that strain WS11T formed an independent monophyletic branch in the family Rhizobiaceae, paralleled with the species in the families Brucellaceae and Phyllobacteriaceae within the order Rhizobiales. Cells were Gram-stain-negative, oxidase- and catalase-positive, and aerobic short rods (1.5-2.4×0.9-1.0 µm). Growth was observed at salinities ranging from 0 to 5% (optimum, 1 %), from pH 6.5 to 9 (optimum, pH 7) and at temperatures between 20 and 30 °C (optimum, 28 °C). Strain WS11T was piezotolerant, growing optimally at 0.1 MPa (range 0.1-70 MPa). The main fatty acid was summed feature 8 (C18 : 1 ω7c/C18  : 1 ω 6c). The sole respiratory quinone was ubiquinone-10 (Q-10). The predominant polar lipids were phosphatidylcholine, two unidentified aminophospholipids and an unidentified phospholipid. The genome size was about 4.36 Mbp and the G+C content was 62.3 mol%. The combined genotypic and phenotypic data show that strain WS11T represents a novel species of a novel genus in the family Rhizobiaceae, for which the name Georhizobium profundi gen. nov., sp. nov. is proposed (type strain WS11T=MCCC 1K03498T=KCTC 62439T).

Genome analysis of deep sea piezotolerant Nesiotobacter exalbescens COD22 and toluene degradation studies under high pressure condition

A marine isolate, Nesiotobacter exalbescens COD22, isolated from deep sea sediment (2100 m depth) was capable of degrading aromatic hydrocarbons. The Nesiotobacter sp. grew well in the presence of toluene at 0.1 MPa and 10 MPa at a rate of 0.24 h^-1 and 0.12 h^-1, respectively, in custom designed high pressure reactors. Percentage of hydrocarbon degradation was found to be 87.5% at ambient pressure and it reached 92% under high pressure condition within a short retention period of 72 h. The biodegradation of hydrocarbon was confirmed by the accumulation of dicarboxylic acid, benzoic acid, benzyl alcohol and benzaldehyde which are key intermediates in toluene catabolism. The complete genome sequence consists of 4,285,402 bp with 53% GC content and contained 3969 total coding genes. The complete genome analysis revealed unique adaptation and degradation capabilities for complex aromatic compounds, biosurfactant synthesis to facilitate hydrocarbon emulsification, advanced mechanisms for chemotaxis and presence of well developed flagellar assembly. The genomic data corroborated with the results of hydrocarbon biodegradation at high pressure growth conditions and confirmed the biotechnological potential of Nesiotobacter sp. towards bioremediation of hydrocarbon polluted deep sea environments.

Physiological and genomic features of Paraoceanicella profunda gen. nov., sp. nov., a novel piezophile isolated from deep seawater of the Mariana Trench

A novel piezophilic alphaproteobacterium, strain D4M1^T, was isolated from deep seawater of the Mariana Trench. 16S rRNA gene analysis showed that strain D4M1^T was most closely related to Oceanicella actignis PRQ‐67^T (94.2%), Oceanibium sediminis O448^T (94.2%), and Thioclava electrotropha ElOx9^T (94.1%). Phylogenetic analyses based on both 16S rRNA gene and genome sequences showed that strain D4M1^T formed an independent monophyletic branch paralleled with the genus Oceanicella in the family Rhodobacteraceae. Cells were Gram‐stain‐negative, aerobic short rods, and grew optimally at 37°C, pH 6.5, and 3.0% (w/v) NaCl. Strain D4M1^T was piezophilic with the optimum pressure of 10 MPa. The principal fatty acids were C_18:1ω7c/C_18:1ω6c and C_16:0, major respiratory quinone was ubiquinone‐10, and predominant polar lipids were phosphatidylglycerol, phosphatidylethanolamine, and an unidentified aminophospholipid. The complete genome contained 5,468,583‐bp with a G + C content of 70.2 mol% and contained 4,855 protein‐coding genes and 78 RNA genes. Genomic analysis revealed abundant clues on bacterial high‐pressure adaptation and piezophilic lifestyle. The combined evidence shows that strain D4M1^T represents a novel species of a novel genus in the family Rhodobacteraceae, for which the name Paraoceanicella profunda gen. nov., sp. nov. is proposed (type strain D4M1^T = MCCC 1K03820^T = KCTC 72285^T).

Polyphasic taxonomic analysis of Parasedimentitalea marina gen. nov., sp. nov., a psychrotolerant bacterium isolated from deep sea water of the New Britain Trench

A novel Rhodobacteraceae bacterium, strain W43T, was isolated from a deep-sea water sample from the New Britain Trench. Strain W43T exhibited the highest 16S rRNA gene sequence similarity of 96.5% to Sedimentitalea nanhaiensis DSM 24252T, Phaeobacter gallaeciensis DSM 26640T, Phaeobacter inhibens DSM 16374T, and Phaeobacter porticola P97T. Phylogenetic analysis of the 16S rRNA gene and phylogenomic analysis of the genome showed that strain W43T formed an independent monophyletic branch within the family Rhodobacteraceae. Strain W43T was Gram-stain-negative, rod-shaped, and grew optimally at 16-20°C, pH 6.5-7.0 and 2% (w/v) NaCl. The principal fatty acids were C18:1ω7c/C18:1ω6c, major respiratory quinone was ubiquinone-10 and predominant polar lipids were phosphatidylethanolamine, phosphatidylglycerol and diphosphatidylglycerol. The 5 080 916 bp long genome, comprising a circular chromosome and four plasmids, exhibits a G + C content of 55.9 mol%. The combined phenotypic, chemotaxonomic and molecular data show that strain W43T represents a novel species of a novel genus, for which the name Parasedimentitalea marina gen. nov. sp. nov. is proposed (type strain W43T = MCCC 1K03532T = KCTC 62635T).

A marine plasmid hitchhiking vast phylogenetic and geographic distances

Horizontal gene transfer (HGT) is the movement of genetic material between organisms other than by reproduction, which plays an important role in bacterial evolution. Often, mobile genetic elements such as plasmids are involved in HGT. In this study, we present phylogenetic, biogeographic, and functional analyses of a previously unrecognized plasmid that is found with 100% sequence identity in multiple distinct bacterial genera obtained from geographically separated locations. This is the only known instance where actual nucleotide identity and not only high synteny has been described for plasmids in environmental organisms. Furthermore, we provide experimental evidence for the potential of this plasmid to be transmitted across bacterial orders, thereby increasing our understanding of evolution and microbial niche adaptation in the environment.

Horizontal gene transfer (HGT) plays an important role in bacterial evolution and serves as a driving force for bacterial diversity and versatility. HGT events often involve mobile genetic elements like plasmids, which can promote their own dissemination by associating with adaptive traits in the gene pool of the so-called mobilome. Novel traits that evolve through HGT can therefore lead to the exploitation of new ecological niches, prompting an adaptive radiation of bacterial species. In this study, we present phylogenetic, biogeographic, and functional analyses of a previously unrecognized RepL-type plasmid found in diverse members of the marine Roseobacter group across the globe. Noteworthy, 100% identical plasmids were detected in phylogenetically and geographically distant bacteria, revealing a so-far overlooked, but environmentally highly relevant vector for HGT. The genomic and functional characterization of this plasmid showed a completely conserved backbone dedicated to replication, stability, and mobilization as well as an interchangeable gene cassette with highly diverse, but recurring motifs. The majority of the latter appear to be involved in mechanisms coping with toxins and/or pollutants in the marine environment. Furthermore, we provide experimental evidence that the plasmid has the potential to be transmitted across bacterial orders, thereby increasing our understanding of evolution and microbial niche adaptation in the environment.

Devosia naphthalenivorans sp. nov., isolated from East Pacific Ocean sediment

A Gram-stain-negative bacterium, designated CM5-1^T, was isolated from a sediment sample collected from the East Pacific Ocean. 16S rRNA gene sequence analysis revealed that strain CM5-1^T belongs to the genus Devosia, with closely related type strains Devosia submarina KMM 9415^T (98.6 %), Devosia psychrophilaCr7-05^T (98.6 %) and Devosia psychrophilaE84^T (98.2 %). Up-to-date bacterial core gene set analysis revealed that strain CM5-1^T represents one independent lineage with D. submarina KMM 9415^T. The average nucleotide identity values of CM5-1^T with D. submarina KMM 9415^T and D. psychrophila Cr7-05^T are 80.1 and 77.9 %, respectively. In silico DNA-DNA hybridization values between strain CM5-1^T and D. submarina KMM 9415^T and D. psychrophila Cr7-05^T are 23.8 and 21.9 %, respectively. Strain CM5-1^T contains diphosphatidylglycerol, phosphatidylglycerol and glycolipid as major polar lipids. The sole isoprenoid quinone is ubiquinone-10, and C18 : 1ω7c and 11-methyl C18 : 1ω7c are the dominant cellular fatty acids. The G+C content of the genomic DNA is 61.4 mol%. Differential phylogenetic distinctiveness and chemotaxonomic differences, together with the phenotypic properties observed in this study, revealed that strain CM5-1^T could be differentiated from closely related species. Therefore, we propose strain CM5-1^T as a novel species of the genus Devosia, for which the name Devosia naphthalenivorans sp. nov. is suggested. The type strain is CM5-1^T (=JCM32509^T=CGMCC 1.13553^T).

Sinomicrobium soli sp. nov., isolated from arctic soil

A bacterial strain, designated N-1-3-6T, was isolated from a soil sample collected from the arctic regions. The cells were short rods, Gram-stain-negative, catalase- and oxidase-positive. Growth was observed with 0–12 % (w/v) NaCl, with optimal growth at 0.5–2 %, and at pH 6.0–9.0, with optimum of pH 7.0, and a growth temperature of 10–45 °C, with an optimum of 28–37 °C. Phylogenetic analysis based on the 16S rRNA gene placed N-1-3-6T in the genus Sinomicrobium with the closest relative being Sinomicrobium pectinilyticum 5DNS001T, exhibiting 95.3 % 16S rRNA pairwise similarity. A polyphasic taxonomic study, including phenotypic, chemotaxonomic and molecular analyses, was performed to clarify its taxonomic position. N-1-3-6T contained MK-6 as the predominant menaquinone. Polar lipids consisted of phosphatidylethanolamine and several unidentified aminolipids, phospholipids and lipids. The principal fatty acids (>10 %) were iso-C15 : 0 (26.9 %), summed feature 3 [C16 : ω7c/ω6c (17.2 %)] and iso-C17 : 0 3-OH (14.7 %). The DNA G+C content of N-1-3-6T was 47.7 mol%. On the basis of its phenotypic and genotypic properties, strain N-1-3-6T should be classified as representing a novel species of the genus Sinomicrobium , for which the name Sinomicrobium soli sp. nov. is proposed, with the type strain N-1-3-6T (=MCCC 1A06047T=KCTC 52339T).

Acuticoccus sediminis sp. nov., isolated from deep-sea sediment of the Indian Ocean and proposal of Acuticoccaceae fam. nov

A Gram-staining negative, aerobic, oval-shaped bacterium, designated strain PTG4-2^T, was isolated from deep-sea sediment of the Indian Ocean. Growth was observed with 1-9 % (w/v) NaCl with optimal growth with 3 %, at pH 6.0-10.0 with an optimum of pH 7.0, and at 4-40 °C with an optimum of 30 °C. Positive for catalase and oxidase. The results of a 16S rRNA gene sequence comparison indicated that PTG4-2^T was most closely related to Acuticoccus yangtzensis JL1095^T (97.3 %), followed by Acuticoccus kandeliae J103^T (96.5 %), all other species shared <93 % sequence similarity. The results of phylogenetic analysis based on 16S rRNA gene sequences indicated that PTG4-2^T forms a distinct lineage within the genus Acuticoccus, and revealed that the genus Acuticoccus forms a novel family-level clade in the order Rhizobiales. The ANI and the DNA-DNA hybridization estimate values between PTG4-2^T and two type strains (A. yangtzensis JL1095^T and A. kandeliae J103^T) were 79.9-76.2 % and 23.1-20.8 %, respectively. PTG4-2^T contained Q-10 as the predominant ubiquinone. The principal fatty acids (>5 %) were summed feature 8 [C18 : 1ω7c/ω6c (72.2 %)], C18 : 0 (8.4 %), C20 : 1ω7c (6.4 %) and C16 : 0 (6.3 %). The polar lipids consisted of phosphatidylglycerol, three unidentified phospholipids, two unidentified glycolipids, one unidentified aminolipid and one unknown lipid. The DNA G+C content of PTG4-2^T is 69.2 mol%. On the basis of the polyphasic taxonomic evidence presented in this study, PTG4-2^T should be classified as representing a novel species of the genus Acuticoccus, for which the name Acuticoccus sediminis sp. nov. is proposed, with the type strain PTG4-2^T (=MCCC 1A01274^T=KCTC 52323^T). In addition, a novel family, Acuticoccaceae fam. nov., is proposed to accommodate the genus Acuticoccus.

Marinobacter profundi sp. nov., a slightly halophilic bacterium isolated from a deep-sea sediment sample of the New Britain Trench

A piezotolerant, cold-adapted, slightly halophilic bacterium, designated strain PWS21^T, was isolated from a deep-sea sediment sample collected from the New Britain Trench. Cells were observed to be Gram-stain negative, rod-shaped, oxidase- and catalase-positive. Growth of the strain was observed at 4-45 °C (optimum 37 °C), at pH 5.0-9.0 (optimum 7.0) and in 0.5-20% (w/v) NaCl (optimum 3-4%). The optimum pressure for growth was 0.1 MPa (megapascal) with tolerance up to 70 MPa. 16S rRNA gene sequence analysis showed that strain PWS21^T is closely related to Marinobacter guineae M3B^T (98.4%) and Marinobacter lipolyticus SM19^T (98.2%). Multilocus sequence analysis (MLSA) based on sequences of housekeeping genes gyrB, recA, atpD, rpoB and rpoD indicates that strain PWS21^T represents a distinct evolutionary lineage within the genus Marinobacter. Furthermore, strain PWS21^T showed low ANI and diDDH values to the closely related species. The principal fatty acids were identified as C_12:0, C_12:0 3-OH, C_16:1ω9c, C_16:0 and C_18:1ω9c. Ubiquinone-9 was identified as the major respiratory quinone. The polar lipids were identified as phosphatidylethanolamine (PE), phosphatidylglycerol (PG), diphosphatidylglycerol (DPG), aminophospholipid (APL), two unidentified lipids and an unidentified phospholipid (PL). The G + C content of the genomic DNA was determined to be 60.3 mol%. On the basis of phenotypic, chemotaxonomic and molecular data, we conclude that strain PWS21^T represents a novel species of the genus Marinobacter, for which the name Marinobacter profundi sp. nov. is proposed (type strain PWS21^T = KCTC 52990^T = MCCC 1K03345^T).

Complete Genome Sequence of Celeribacter baekdonensis Strain LH4, a Thiosulfate-Oxidizing Alphaproteobacterial Isolate from Gulf of Mexico Continental Slope Sediments

We report here the closed genome sequences of Celeribacter baekdonensis strain LH4 and five unnamed plasmids obtained through PacBio sequencing with 99.99% consensus concordance. The genomes contained several distinctive features not found in other published Celeribacter genomes, including the potential to aerobically degrade styrene and other phenolic compounds.

Patterns of Endemism and Habitat Selection in Coalbed Microbial Communities

Microbially produced methane, a versatile, cleaner-burning alternative energy resource to fossil fuels, is sourced from a variety of natural and engineered ecosystems, including marine sediments, anaerobic digesters, shales, and coalbeds. There is a prevailing interest in developing environmental biotechnologies to enhance methane production. Here, we use small-subunit rRNA gene sequencing and metagenomics to better describe the interplay between coalbed methane (CBM) well conditions and microbial communities in the Alberta Basin. Our results show that CBM microbial community structures display patterns of endemism and habitat selection across the Alberta Basin, consistent with observations from other geographical locations. While some phylum-level taxonomic patterns were observed, relative abundances of specific taxonomic groups were localized to discrete wells, likely shaped by local environmental conditions, such as coal rank and depth-dependent physicochemical conditions. To better resolve functional potential within the CBM milieu, a metagenome from a deep volatile-bituminous coal sample was generated. This sample was dominated by Rhodobacteraceae genotypes, resolving a near-complete population genome bin related to Celeribacter sp. that encoded metabolic pathways for the degradation of a wide range of aromatic compounds and the production of methanogenic substrates via acidogenic fermentation. Genomic comparisons between the Celeribacter sp. population genome and related organisms isolated from different environments reflected habitat-specific selection pressures that included nitrogen availability and the ability to utilize diverse carbon substrates. Taken together, our observations reveal that both endemism and metabolic specialization should be considered in the development of biostimulation strategies for nonproductive wells or for those with declining productivity.

Celeribacter naphthalenivorans sp. nov., a naphthalene-degrading bacterium from tidal flat sediment

A Gram-stain-negative, aerobic and moderately halophilic bacterium, designated strain EMB201T, was isolated from tidal flat sediment of the South Sea in Korea. Cells were motile rods with a single polar flagellum and had catalase- and oxidase-positive activities. Growth of strain EMB201T was observed at 15–37 °C (optimum, 30 °C), at pH 5.0–9.5 (optimum, pH 7.0–7.5) and in the presence of 1–7 % (w/v) NaCl (optimum, 2–3 %). Strain EMB201T contained ubiquinone-10 as the sole isoprenoid quinone and summed feature 8 (comprising C18 : 1ω7c/ω6c), C18 : 0ω7c 11-methyl and C10 : 0 3-OH as the major fatty acids. Phosphatidylglycerol and an unidentified amino lipid were identified as the major polar lipids and an unidentified phospholipid and three unidentified lipids were detected as minor components. The G+C content of the genomic DNA was approximately 58.4 mol%. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain EMB201T formed a phylogenetic lineage with members of the genus Celeribacter. Strain EMB201T was related most closely to Celeribacter halophilus ZXM137T with a 16S rRNA gene sequence similarity of 98.3 %, and the level of DNA–DNA relatedness between the two strains was 17.0 ± 2.0 %. The combined chemotaxonomic and molecular properties suggest that strain EMB201T represents a novel species of the genus Celeribacter, for which the name Celeribacter naphthalenivorans sp. nov. is proposed. The type strain is EMB201T ( = KACC 18393T = JCM 30679T).

Polycyclic aromatic hydrocarbons in deep sea sediments: Microbe-pollutant interactions in a remote environment

Recalcitrant polycyclic aromatic hydrocarbons (PAHs) released into seawater end up in the deep sea sediments (DSSs). However, their fate here is often oversimplified by theoretical models. Biodegradation of PAHs in DSSs, is assumed to be similar to biodegradation in surface habitats, despite high hydrostatic pressures and low temperatures that should significantly limit PAH biodegradation. Bacteria residing in the DSSs (related mainly to α- and γ-Proteobacteria) have been shown to or predicted to possess distinct genes, enzymes and metabolic pathways, indicating an adaptation of these bacterial communities to the psychro-peizophilic conditions of the DSSs. This work summarizes some of the most recent research on DSS hydrocarbonoclastic populations and mechanisms of PAH degradation and discusses the challenges posed by future high CO2 and UV climate scenarios on biodegradation of PAHs in DSSs.

Celeribacter manganoxidans sp. nov., a manganese-oxidizing bacterium isolated from deep-sea sediment of a polymetallic nodule province

A Gram-stain-negative, strictly aerobic, non-motile, rod-shaped, manganese-oxidizing bacterial strain, designated DY2-5T, was isolated from surface sediment of Pacific Clarion-Clipperton Fracture Zone (CCFZ). Growth occurred at 0-37 °C (optimum 28 °C), pH 6.5-9.0 (optimum pH 7.0-7.5) and in the presence of 1-11% (w/v) NaCl (optimum 3-4%). Phylogenetic analysis based on 16S rRNA gene sequences revealed that the novel strain was most closely related to Celeribacter halophilus ZXM137T with 96.13% sequence similarity, and had 16S rRNA gene sequence similarities in the range 93.89-95.87% with other species of the genus Celeribacter. The dominant fatty acids were summed feature 8 (C18:1ω7c and/or C18:1ω6c) and C16:0. The polar lipids of strain DY2-5T comprised phosphatidylglycerol, phosphatidylcholine and two unknown aminolipids. The major respiratory quinone was ubiquinone-10 (Q-10). The DNA G+C content of strain DY2-5T was 64.8 mol%. On the basis of the phenotypic, genotypic and physiological evidence, strain DY2-5T represents a novel species of the genus Celeribacter, for which the name Celeribacter manganoxidans sp. nov. is proposed. The type strain is DY2-5T ( = JCM 19384T = KCTC 32473T).

Genomic and metabolic analysis of fluoranthene degradation pathway in Celeribacter indicus P73T

Celeribacter indicus P73(T), isolated from deep-sea sediment from the Indian Ocean, is capable of degrading a wide range of polycyclic aromatic hydrocarbons (PAHs) and is the first fluoranthene-degrading bacterium within the family Rhodobacteraceae. Here, the complete genome sequence of strain P73(T) is presented and analyzed. Besides a 4.5-Mb circular chromosome, strain P73(T) carries five plasmids, and encodes 4827 predicted protein-coding sequences. One hundred and thirty-eight genes, including 14 dioxygenase genes, were predicted to be involved in the degradation of aromatic compounds, and most of these genes are clustered in four regions. P73_0346 is the first fluoranthene 7,8-dioxygenase to be discovered and the first fluoranthene dioxygenase within the toluene/biphenyl family. The degradative genes in regions B and D in P73(T) are absent in Celeribacter baekdonensis B30, which cannot degrade PAHs. Four intermediate metabolites [acenaphthylene-1(2H)-one, acenaphthenequinone, 1,2-dihydroxyacenaphthylene, and 1,8-naphthalic anhydride] of fluoranthene degradation by strain P73(T) were detected as the main intermediates, indicating that the degradation of fluoranthene in P73(T) was initiated by dioxygenation at the C-7,8 positions. Based on the genomic and metabolitic results, we propose a C-7,8 dioxygenation pathway in which fluoranthene is mineralized to TCA cycle intermediates.