Bacterial Population Changes during the Degradation Process of a Lactate (LA)-Enriched Biodegradable Polymer in River Water: LA-Cluster Preferable Bacterial Consortium

The lactate-based polyester poly[lactate (LA)-co-3-hydroxybutyrate (3HB)], termed LAHB, is a highly transparent and flexible bio-based polymeric material. There are many unknowns regarding its degradation process in riverine environments, especially the changes in bacterial flora that might result from its degradation and the identities of any LAHB-degrading bacteria. LAHB were immersed in the river water samples (A and B), and LAHB degradation was observed in terms of the weight change of the polymer and the microscopic changes on the polymer surfaces. A metagenomic analysis of microorganisms was conducted to determine the effect of LAHB degradation on the aquatic environment. The bacterial flora obtained from beta diversity analysis differed between the two river samples. The river A water sample showed the simultaneous degradation of LA and 3HB even though the copolymer was LA-enriched, suggesting preferable hydrolysis of the LA-enriched segments. In contrast, only 3HB degraded for the LAHB in the river B water sample. The linear discriminant analysis effect size (LEfSe) analysis revealed 14 bacteria that were significantly increased in the river A water sample during LAHB degradation, suggesting that these bacteria preferentially degraded and assimilated LA-clustering polymers. Our metagenomic analysis provides useful insights into the dynamic changes in microbial communities and LA-clustering polymer-degrading bacteria.

Dynamics of PHA-Accumulating Bacterial Communities Fed with Lipid-Rich Liquid Effluents from Fish-Canning Industries

The biosynthesis of polyhydroxyalkanoates (PHAs) from industrial wastes by mixed microbial cultures (MMCs) enriched in PHA-accumulating bacteria is a promising technology to replace petroleum-based plastics. However, the populations' dynamics in the PHA-accumulating MMCs are not well known. Therefore, the main objective of this study was to address the shifts in the size and structure of the bacterial communities in two lab-scale sequencing batch reactors (SBRs) fed with fish-canning effluents and operated under non-saline (SBR-N, 0.5 g NaCl/L) or saline (SBR-S, 10 g NaCl/L) conditions, by using a combination of quantitative PCR and Illumina sequencing of bacterial 16S rRNA genes. A double growth limitation (DGL) strategy, in which nitrogen availability was limited and uncoupled to carbon addition, strongly modulated the relative abundances of the PHA-accumulating bacteria, leading to an increase in the accumulation of PHAs, independently of the saline conditions (average 9.04 wt% and 11.69 wt%, maximum yields 22.03 wt% and 26.33% SBR-N and SBR-S, respectively). On the other hand, no correlations were found among the PHAs accumulation yields and the absolute abundances of total Bacteria, which decreased through time in the SBR-N and did not present statistical differences in the SBR-S. Acinetobacter, Calothrix, Dyella, Flavobacterium, Novosphingobium, Qipengyuania, and Tsukamurella were key PHA-accumulating genera in both SBRs under the DGL strategy, which was revealed as a successful tool to obtain a PHA-enriched MMC using fish-canning effluents.

Genomic Insights into Denitrifying Methane-Oxidizing Bacteria Gemmobacter fulva sp. Nov., Isolated from an Anabaena Culture

The genus Gemmobacter grows phototrophically, aerobically, or anaerobically, and utilizes methylated amine. Here, we present two high-quality complete genomes of the strains con4 and con5^T isolated from a culture of Anabaena. The strains possess sMMO (soluble methane monooxygenase)-oxidizing alkanes to carbon dioxide. Functional genes for methane-oxidation (prmAC, mimBD, adh, gfa, fdh) were identified. The genome of strain con5^T contains nirB, nirK, nirQ, norB, norC, and norG genes involved in dissimilatory nitrate reduction. The presence of nitrite reductase gene (nirK) and the nitric-oxide reductase gene (norB) indicates that it could potentially use nitrite as an electron acceptor in anoxic environments. Taxonomic investigations were also performed on two strains through polyphasic methods, proposing two isolates as a novel species of the genus Gemmobacter. The findings obtained through the whole genome analyses provide genome-based evidence of complete oxidation of methane to carbon dioxide. This study provides a genetic blueprint of Gemmobacter fulva con5^T and its biochemical characteristics, which help us to understand the evolutionary biology of the genus Gemmobacter.

Comparative genomics analyses indicate differential methylated amine utilization trait within members of the genus Gemmobacter

Methylated amines are ubiquitous in the environment and play a role in regulating the earth's climate via a set of complex biological and chemical reactions. Microbial degradation of these compounds is thought to be a major sink. Recently we isolated a facultative methylotroph, Gemmobacter sp. LW-1, an isolate from the unique environment Movile Cave, Romania, which is capable of methylated amine utilization as a carbon source. Here, using a comparative genomics approach, we investigate how widespread methylated amine utilization is within members of the bacterial genus Gemmobacter. Seven genomes of different Gemmobacter species isolated from diverse environments, such as activated sludge, fresh water, sulphuric cave waters (Movile Cave) and the marine environment were available from the public repositories and used for the analysis. Our results indicate that methylamine utilization is a distinctive feature of selected members of the genus Gemmobacter, namely G. aquatilis, G. lutimaris, G. sp. HYN0069, G. caeni and G. sp. LW-1 have the genetic potential while others (G. megaterium and G. nectariphilus) have not.

Falsigemmobacter faecalis gen. nov. sp. nov., isolated from faeces of Rhinopithecus roxellanae, and reclassification of Gemmobacter intermedius as Falsigemmobacter intermedius comb. nov

Strain YIM 102744-1^T was isolated from Rhinopithecus roxellanae fecal sample collected at Yunnan Wild Animal Park, Yunnan province, PR China. Cells were Gram-stain-negative, aerobic, non-motile and irregular rods. Optimal growth occurred in the presence of 0-1.0% (w/v) NaCl, at pH 7.0-8.0, and at 30 °C. The predominant ubiquinone was Q-10. The major cellular fatty acids (> 10.0%) were C_18:1ω7c and C_16:1ω7c/C_16:1ω6c. The dominant polar lipids were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine and phosphatidylcholine. The DNA G + C content was 62.4 mol%. Phylogenetic analysis based on 16S rRNA gene sequences revealed that YIM 102744-1^T belonged to the family Rhodobacteraceae and shared the highest similarity with the type strain Gemmobacter intermedius 119/4^T (96.6%). In addition, phylogenetic trees indicated that strain YIM 102744-1^T formed a distinct clade together with the closest relative G. intermedius 119/4^T. Based on the results of polyphasic taxonomic analysis, strain YIM 102744-1^T is considered to represent a novel species within a new genus Falsigemmobacter, for which the name Falsigemmobacter faecalis gen. nov., sp. nov. is proposed. The type strain of Falsigemmobacter faecalis is YIM 102744-1^T(= KCTC 52106^T = CCTCC AB 2016031^T). Because Gemmobacter intermedius 119/4^T formed a branch with YIM 102744-1 in the phylogenetic trees and was clearly separated from the other members within the genus Gemmobacter, it is also proposed to transfer into the genus Falsigemmobacter as Falsigemmobacter intermedius comb. nov. (type strain 119/4^T = CIP 110795^T = LMG 28215^T = CCM 8510^T). The type species of the genus Falsigemmobacter is Falsigemmobacter intermedius gen. nov., comb. nov.

Gemmobacter serpentinus sp. nov., isolated from conserved forages

A Gram-stain-negative, long-rod-shaped and facultative aerobic bacterium, designated HB-1T, was isolated from a round hay bale at the Kansas State University Beef Stocker Unit. The results of phylogenetic analysis of 16S rRNA gene sequences indicated that strain HB-1T clustered within the genus Gemmobacter and its closest relatives were Gemmobacter aquaticus A1-9T (98.0 %), Gemmobacter lutimaris YJ-T1-11T (98.0 %), Gemmobacter fontiphilus JS43T (97.8 %), Gemmobacter aquatilis DSM 3857T (97.5 %) and Gemmobacter lanyuensis Orc-4T (96.9 %). Additional phylogenomic analysis also indicated that strain HB-1T belongs to the genus Gemmobacter . The draft genome of strain HB-1T had a total length of 4.23 Mbp and contained 4071 protein-coding genes. The average nucleotide identity values between the genomes of strain HB-1T and the three most-related type strains ranged from 77.5 to 78.1 %. The DNA G+C content of strain HB-1T was 63.7 mol%. The novel strain grew at 10–37 °C, pH 5–10 and with 0–2 % NaCl. Oxidase and catalase activities were positive. Cells were 0.3–0.4 µm wide, 3.0–7.0 µm long and usually found in pairs or chains of cells. The major respiratory quinone of strain HB-1T was Q-10 (90 %), with a minor amount of Q-9 (10 %). The major fatty acids were C18 : 1  ω7c (54.6 %) and C16 : 0 (18.2 %). On the basis of phenotypic, phylogenetic and chemotaxonomic data, strain HB-1T (=DSM 109828T=ATCC TSD-211T) is considered to represent a novel species of the genus Gemmobacter , for which the name Gemmobacter serpentinus sp. nov. is proposed.

Gemmobacter caeruleus sp. nov., a novel species originating from lake sediment

An aerobic, Gram-stain-negative, non-spore-forming and rod-shaped bacterial strain, designated N8T, was isolated from the interfacial sediment of Taihu Lake in PR China. The strain formed white to blue colonies on R2A agar. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain N8T represented a member of the genus Gemmobacter and was most closely related to Gemmobacter aquaticus A1-9T (97.97 %). The average nucleotide identity and digital DNA–DNAhybridization values between strain N8T and G. aquaticus A1-9T based on their whole genomes were 78.8 and 21.7 %, respectively. Q-10 was the main predominant ubiquinone. The major fatty acids were summed feature 8 (C18 : 1ω7c and/or C18 : 1ω6c), C18 : 0 and C16 : 0. The G+C content of the genomic DNA was 66.1 mol%. The polar lipids comprised phosphatidylethanolamine, phosphatidylglycerol, phosphatidylcholine, one unidentified phospholipid, two unidentified glycolipids and two unidentified lipids. Based on its physiological, biochemical and chemotaxonomic characteristics, strain N8T represents a novel species of the genus Gemmobacter , for which the name Gemmobacter caeruleus sp. nov. is proposed. The type strain is N8T=(KACC 21307T=MCCC 1K04036T).

Taxogenomics Resolves Conflict in the Genus Rhodobacter: A Two and Half Decades Pending Thought to Reclassify the Genus Rhodobacter

The genus Rhodobacter is taxonomically well studied, and some members are model organisms. However, this genus is comprised of a heterogeneous group of members. 16S rRNA gene-based phylogeny of the genus Rhodobacter indicates a motley assemblage of anoxygenic phototrophic bacteria (genus Rhodobacter) with interspersing members of other genera (chemotrophs) making the genus polyphyletic. Taxogenomics was performed to resolve the taxonomic conflicts of the genus Rhodobacter using twelve type strains. The phylogenomic analysis showed that Rhodobacter spp. can be grouped into four monophyletic clusters with interspersing chemotrophs. Genomic indices (ANI and dDDH) confirmed that all the current species are well defined, except Rhodobacter megalophilus. The average amino acid identity values between the monophyletic clusters of Rhodobacter members, as well as with the chemotrophic genera, are less than 80% whereas the percentage of conserved proteins values were below 70%, which has been observed among several genera related to Rhodobacter. The pan-genome analysis has shown that there are only 1239 core genes shared between the 12 species of the genus Rhodobacter. The polyphasic taxonomic analysis supports the phylogenomic and genomic studies in distinguishing the four Rhodobacter clusters. Each cluster is comprised of one to seven species according to the current Rhodobacter taxonomy. Therefore, to address this taxonomic discrepancy we propose to reclassify the members of the genus Rhodobacter into three new genera, Luteovulum gen. nov., Phaeovulum gen. nov. and Fuscovulum gen. nov., and provide an emended description of the genus Rhodobacter sensu stricto. Also, we propose reclassification of Rhodobacter megalophilus as a sub-species of Rhodobacter sphaeroides.

Gemmobacter intermedius sp. nov., isolated from a white stork (Ciconia ciconia)

A cream-coloured, Gram-stain-negative, aerobic, non-motile, rod- to irregular shaped bacterium, strain 119/4T, was isolated from a choana swab of a white stork nestling on sheep blood agar. 16S rRNA gene sequence analysis and subsequent comparisons showed that it was a member of the family Rhodobacteraceae, showing 94.9 % similarity to the type strain of Gemmobacter tilapiae and 94.6 % similarity to that of Gemmobacter nectariphilus , but also similarly low sequence similarity to the type strains of Rhodobacter viridis (94.8 %), Rhodobacter veldkampii (94.6 %) and Paenirhodobacter enshiensis (94.6 %). Reconstruction of phylogenetic trees showed that strain 119/4T clustered close to species of the genus Gemmobacter . The quinone system contained high amounts of ubiquinone Q-10 with traces of Q-8, Q-9 and Q-11, and the fatty acid profile consisted mainly of C18 : 1ω7c, C16 : 1ω7c/iso-C15 : 0 2-OH and C10 : 0 3-OH. The predominant polar lipids were diphosphatidylglycerol, phosphatidylethanolamine, phoshatidylglycerol and phosphatidylcholine. Major polyamines were putrescine and spermidine. On the basis of 16S rRNA gene sequence analysis and chemotaxonomic and physiological data, strain 119/4T represents a novel species of the genus Gemmobacter , for which the name Gemmobacter intermedius sp. nov. is proposed. The type strain is 119/4T ( = CIP 110795T = LMG 28215T = CCM 8510T).

Gemmobacter megaterium sp. nov., isolated from coastal planktonic seaweeds

A Gram-stain-negative, non-motile and aerobic bacterium, designated CF17T, was isolated from coastal planktonic seaweeds, East China Sea. The isolate grew at 18–37 °C (optimum 25–28 °C), pH 6.5–9.0 (optimum 7.0–8.0) and with 0–5 % NaCl (optimum 1–2 %, w/v) and 0.5–10 % sea salts (optimum 2–3 %, w/v). Growth of strain CF17T could be stimulated prominently by supplementing the growth medium with the autoclaved supernatant of a culture of strain CF5, which was isolated from the same sample along with strain CF17T. The cell morphology of strain CF17T was a bean-shaped rod consisting of a swollen end and a long prostheca. The phylogenetic analysis of 16S rRNA gene sequences indicated that strain CF17T clustered with Gemmobacter nectariphilus DSM 15620T within the genus Gemmobacter . The DNA G+C content of strain CF17T was 61.4 mol%. The respiratory quinone was ubiquinone Q-10. The major fatty acids included C18 : 1ω7c and C18 : 0. The polar lipids of strain CF17T consisted of phosphatidylethanolamine, phosphatidylglycerol, phosphatidylcholine, two uncharacterized phospholipids, one uncharacterized aminolipid, three uncharacterized glycolipids and one uncharacterized lipid. On the basis of phenotypic, phylogenetic and chemotaxonomic data, strain CF17T ( = CGMCC 1.11024T = JCM 18498T) is considered to represent a novel species of the genus Gemmobacter , for which the name Gemmobacter megaterium sp. nov. is proposed.

Gemmobacter lanyuensis sp. nov., isolated from a freshwater spring

A bacterial strain designated Orc-4T was isolated from a freshwater spring in Taiwan and characterized using the polyphasic taxonomic approach. Cells of strain Orc-4T were facultatively anaerobic, Gram-reaction-negative, poly-β-hydroxybutyrate-accumulating, non-motile rods surrounded by a thick capsule and forming cream–white colonies. Growth occurred at 15–40 °C (optimum, 25–30 °C), at pH 6.0–9.0 (optimum, pH 7.0) and with 0–1 % NaCl (optimum, 0–0.5 %). Phylogenetic analyses based on 16S rRNA gene sequences showed that strain Orc-4T belonged to the genus Gemmobacter within the family Rhodobacteraceae of the class Alphaproteobacteria and its most closely related neighbour was Gemmobacter fontiphilus JS43T with sequence similarity of 97.8 %. Strain Orc-4T contained C18 : 1ω7c as the predominant fatty acid. The major respiratory quinone was Q-10. The DNA G+C content of the genomic DNA was 63.5 mol%. The polar lipid profile consisted of a mixture of phosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine, one uncharacterized aminolipid and several uncharacterized phospholipids. The DNA–DNA relatedness of strain Orc-4T with respect to recognized species of the genus Gemmobacter was less than 48 %. On the basis of the genotypic, chemotaxonomic and phenotypic data, strain Orc-4T represents a novel species of the genus Gemmobacter , for which the name Gemmobacter lanyuensis sp. nov. is proposed. The type strain is Orc-4T ( = BCRC 80378T = LMG 26667T = KCTC 23714T).