The familyErythrobacteraceae, belonging to the orderSphingomonadales, classAlphaproteobacteria, is globally distributed in various environments. Currently, this family consist of seven genera:Altererythrobacter,Croceibacterium,Croceicoccus,Erythrobacter,Erythromicrobium,PorphyrobacterandQipengyuania. As more species are identified, the taxonomic status of the familyErythrobacteraceaeshould be revised at the genomic level because of its polyphyletic nature evident from 16S rRNA gene sequence analysis. Phylogenomic reconstruction based on 288 single-copy orthologous clusters led to the identification of three separate clades. Pairwise comparisons of average nucleotide identity, average amino acid identity (AAI), percentage of conserved protein and evolutionary distance indicated that AAI and evolutionary distance had the highest correlation. Thresholds for genera boundaries were proposed as 70 % and 0.4 for AAI and evolutionary distance, respectively. Based on the phylo-genomic and genomic similarity analysis, the three clades were classified into 16 genera, including 11 novel ones, for which the namesAlteraurantiacibacter,Altericroceibacterium,Alteriqipengyuania,Alteripontixanthobacter,Aurantiacibacter,Paraurantiacibacter,Parerythrobacter,Parapontixanthobacter,Pelagerythrobacter,TsuneonellaandPontixanthobacterare proposed. We reclassified all species ofErythromicrobiumandPorphyrobacteras species ofErythrobacter. This study is the first genomic-based study of the familyErythrobacteraceae, and will contribute to further insights into the evolution of this family.

Low-density polyethylene (LDPE), which accounts for 20% of the global plastic production, is discharged in great quantities into the ocean, threatening marine life and ecosystems. Marine microorganisms have previously been reported to degrade LDPE plastics; however, the exploration of strains and enzymes that degrade LDPE is still limited. Here, an LDPE-degrading bacterium was isolated from seawater of the Changjiang Estuary, China and identified as Rhodococcus sp. C-2, the relative abundance of which was dramatically enhanced during PE-degrading microbial enrichment. The strain C-2 exhibited the degradation of LDPE films, leading to their morphological deterioration, reduced hydrophobicity and tensile strength, weight loss, as well as the formation of oxygen-containing functional groups in short-chain products. Sixteen bacterial enzymes potentially involved in LDPE degradation were screened using genomic, transcriptomic, and degradation product analyses. Thereinto, the glutathione peroxidase GPx with exposed active sites catalyzed the LDPE depolymerization with the cooperation of its dissociated superoxide anion radicals. Furthermore, an LDPE degradation model involving multiple enzymes was proposed. The present study identifies a novel PE-degrading enzyme (PEase) for polyethylene bioremediation and promotes the understanding of LDPE degradation.

The members of the phylum Bacteroidetes are recognized as some of the most important specialists for the degradation of polysaccharides. However, in contrast to research on Bacteroidetes in the human gut, research on polysaccharide degradation by marine Bacteroidetes is still rare. The genus Algibacter belongs to the Flavobacteriaceae family of the Bacteroidetes , and most species in this genus are isolated from or near the habitat of algae, indicating a preference for the complex polysaccharides of algae. In this work, a novel brown-seaweed-degrading strain designated HZ22 was isolated from the surface of a brown seaweed ( Laminaria japonica ). On the basis of its physiological, chemotaxonomic, and genotypic characteristics, it is proposed that strain HZ22 represents a novel species in the genus Algibacter with the proposed name Algibacter alginolytica sp. nov. The genome of strain HZ22, the type strain of this species, harbors 3,371 coding sequences (CDSs) and 255 carbohydrate-active enzymes (CAZymes), including 104 glycoside hydrolases (GHs) and 18 polysaccharide lyases (PLs); this appears to be the highest proportion of CAZymes (∼7.5%) among the reported strains in the class Flavobacteria . Seventeen polysaccharide utilization loci (PUL) are predicted to be specific for marine polysaccharides, especially algal polysaccharides from red, green, and brown seaweeds. In particular, PUL N is predicted to be specific for alginate. Taking these findings together with the results of assays of crude alginate lyases, we prove that strain HZ22 ^T can completely degrade alginate. This work reveals that strain HZ22 ^T has good potential for the degradation of algal polysaccharides and that the structure and related mechanism of PUL in strain HZ22 ^T are worth further research.

Two Gram-negative, motile, aerobic bacterial strains, designated B2^T and 1_C16_27^T, were respectively isolated from a seawater sample collected from the East China Sea and a semi-coke sample from north-eastern Estonia. Their genetic, phenotypic and chemotaxonomic properties were studied. The isolates were short rods with polar flagella and were positive for catalase and oxidase activities. Q-10 was the predominant respiratory ubiquinone. The major polar lipids were phosphatidylglycerol, diphosphatidylglycerol and two unidentified glycolipids. The major fatty acids were nonadecanoic (C_19 : 0 cyclo), octadecanoic (C_18 : 0 and C_18 : 0 3-OH), octadecenoic (C_18 : 1) and hexadecanoic (C_16 : 0) acids. The G+C content of the genomic DNA was 58.1–59.3 mol%. 16S rRNA gene sequence analysis revealed that the two isolates represent a distinct lineage within the family Hyphomicrobiaceae. The phylogenetically closest relatives were Cucumibacter (92.7–93.7 % 16S rRNA gene sequence similarity), Devosia (92.9–94.4 %) and Zhangella (91.7–92.1 %). Differential phenotypic properties, together with phylogenetic and genetic distinctiveness, revealed that strains B2^T and 1_C16_27^T could be differentiated from each other and from members of the genera Cucumibacter, Devosia and Zhangella. Therefore, it is proposed that strains B2^T and 1_C16_27^T represent two novel species in a new genus, for which the names Pelagibacterium halotolerans gen. nov., sp. nov. (the type species; type strain B2^T = CGMCC 1.7692^T = JCM 15775^T) and Pelagibacterium luteolum sp. nov. (type strain 1_C16_27^T = CGMCC 1.10267^T = JCM 16552^T = CELMS EEUT 1C1627^T) are proposed.

A Gram-negative, aerobic, neutrophilic, coccoid bacterium, strain E4A9^T, was isolated from a deep-sea sediment sample collected from the East Pacific polymetallic nodule region. 16S rRNA gene sequence analysis showed that the isolate was related to the type strain of Altererythrobacter epoxidivorans (96.0 % sequence similarity). Lower 16S rRNA gene sequence similarities were observed with other members of the genera Altererythrobacter (94.7 %), Erythrobacter (94.0–95.4 %), Erythromicrobium (94.8 %) and Porphyrobacter (94.6–95.1 %) of the family Erythrobacteraceae. Phylogenetic analysis including all described species of the family Erythrobacteraceae and several members of the family Sphingomonadaceae revealed that the isolate formed a distinct phylogenetic lineage with the family Erythrobacteraceae. Chemotaxonomic analysis revealed ubiquinone-10 as the predominant respiratory quinone, anteiso-C_15 : 0, iso-C_14 : 0 and iso-C_15 : 0 as major fatty acids, and phosphatidylglycerol as the major polar lipid. The DNA G+C content was 71.5 mol%. The isolate contained carotenoids, but no bacteriochlorophyll a. On the basis of phenotypic and genotypic data presented in this study, strain E4A9^T represents a novel species in a new genus in the family Erythrobacteraceae for which the name Croceicoccus marinus gen. nov., sp. nov. is proposed; the type strain is E4A9^T (=CGMCC 1.6776^T=JCM 14846^T).

Background: Ferromanganese nodule-bearing deep-sea sediments cover vast areas of the ocean floor, representing a distinctive habitat in the abyss. These sediments harbor unique conditions characterized by high iron concentration and low degradable nutrient levels, which pose challenges to the survival and growth of most microorganisms. While the microbial diversity in ferromanganese nodule-associated sediments has been surveyed several times, little is known about the functional capacities of the communities adapted to these unique habitats. Results: Seven sediment samples collected adjacent to ferromanganese nodules from the Clarion–Clipperton Fracture Zone (CCFZ) in the eastern Pacific Ocean were subjected to metagenomic analysis. As a result, 179 high-quality metagenome-assembled genomes (MAGs) were reconstructed and assigned to 21 bacterial phyla and 1 archaeal phylum, with 88.8% of the MAGs remaining unclassified at the species level. The main mechanisms of resistance to heavy metals for microorganisms in sediments included oxidation (Mn), reduction (Cr and Hg), efflux (Pb), synergy of reduction and efflux (As), and synergy of oxidation and efflux (Cu). Iron, which had the highest content among all metallic elements, may occur mainly as Fe(III) that potentially functioned as an electron acceptor. We found that microorganisms with a diverse array of CAZymes did not exhibit higher community abundance. Instead, microorganisms mainly obtained energy from oxidation of metal (e.g., Mn(II)) and sulfur compounds using oxygen or nitrate as an electron acceptor. Chemolithoautotrophic organisms (Thaumarchaeota and Nitrospirota phyla) were found to be potential manganese oxidizers. The functional profile analysis of the dominant microorganisms further indicated that utilization of inorganic nutrients by redox reactions (rather than organic nutrient metabolism) is a major adaptive strategy used by microorganisms to support their survival in the ferromanganese nodule sediments. Conclusions: This study provides a comprehensive metagenomic analysis of microbes inhabiting metal-rich ferromanganese nodule sediments. Our results reveal extensive redundancy across taxa for pathways of metal resistance and transformation, the highly diverse mechanisms used by microbes to obtain nutrition, and their participation in various element cycles in these unique environments.