Defluviimonas aestuarii sp. nov., a marine bacterium isolated from a tidal flat, and emended description of the genus Defluviimonas Foesel et al. 2011

Polyphasic Taxonomic Analysis of Pontitalea aquivivens gen. nov., sp. nov., Isolated from Seawater

A Gram-stain-negative, rod-shaped, strictly aerobic, non-motile, and chemo-organoheterotrophic alphaproteobacterium, designated KMU-169T, was isolated from coastal seawater in the Republic of Korea. The novel isolate was able to grow at 0-2.0% NaCl concentrations (w/v), pH 6.0-9.5, and 15-40 °C. The analysis based on 16S rRNA gene sequences indicated that strain KMU-169T belongs to the family Paracoccaceae and shared the highest similarity (97.0%) with "Defluviimonas salinarum" CAU 1641T. The major (> 10%) cellular fatty acids were C18:1 ω7c and summed feature 3 (comprising C16:1 ω6c and/or C16:1 ω7c). The predominant respiratory quinone was ubiquinone-10. Strain KMU-169T comprised phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol, phosphatidylcholine, an unidentified aminolipid, an unidentified phospholipid, and an unidentified lipid. The assembled draft genome size of strain KMU-169T was 4.1 Mbp with a DNA G + C content of 65.0%. The average nucleotide identity (ANI), average amino acid identity (AAI), and digital DNA-DNA hybridization (dDDH) values between the genomes of strain KMU-169T and its closely related taxa were 71.9-76.8%, 60.9-76.1%, and 18.4-21.0%, respectively. The genome of the strain KMU-169T revealed the presence of numerous genes involved in bio-macromolecule degradation, indicating a high potential for producing industrially valuable enzymes. Based on the polyphasic taxonomic data reported in this study, a novel genus and a new species of the family Paracoccaceae, for which the name Pontitalea aquivivens gen. nov., sp. nov., is proposed with the type strain KMU-169T (= KCCM 90598T = NBRC 117093T).

Description of Albidovulum litorale sp. nov., Albidovulum marisflavi sp. nov., Albidovulum salinarum sp. nov., and Albidovulum sediminicola sp. nov., and proposal for reclassification of the genus Defluviimonas as a later heterotypic synonym of Albidovulum

Four Gram-stain-negative, aerobic, rod-shaped bacteria, designated WL0002T, WL0024T, WL0050T, and WL0075T, were isolated from sediment in the coastal areas of Nantong City, China. Metagenomic analysis revealed higher relative abundance of taxa closely related to the four strains in sediment (0.79-2.0 %) than in water (0.34-1.3 %) (Mann-Whitney U test: p < 0.001). Phylogenetic analysis based on 16S rRNA gene and the bac120 gene set both suggested that the four strains are closely related to the genus Defluviimonas. Additionally, Albidovulum inexpectatum DSM 12048T formed a distinct branch within Defluviimonas. The evolutionary distance (ED) and percentage of conserved proteins (POCP) analysis indicated that the four strains and the genus strains of Albidovulum and Defluviimonas should be recognized as a single genus. Genomic relatedness analysis among the four strains and type strains of the genera Albidovulum and Defluviimonas was below species delimitation thresholds, except for strains WL0024T and "D. salinarum" CAU 1641T, which should belong to the same species. Based on phenotypic and genotypic characterization, the four strains should be recognized as novel species in Albidovulum, and it is reasonable to reclassify the genus Defluviimonas as a later heterotypic synonym of Albidovulum, consistent with the classification of the Genome Taxonomy Database (GTDB). Four names are proposed as follows: Albidovulum marisflavi sp. nov. (type strain WL0002T = MCCC 1K06013T = JCM 34653T = GDMCC 1.2437T), Albidovulum salinarum sp. nov. (WL0024T = MCCC 1K06062T = JCM 34656T = GDMCC 1.2438T), Albidovulum litorale sp. nov. (WL0050T = MCCC 1K07524T = JCM 35566T = GDMCC 1.3084T), and Albidovulum sediminicola sp. nov. (WL0075T = MCCC 1K06064T = JCM 34660T = GDMCC 1.2419T).

Partitioning of nutrient removal contribution between granules and flocs in a hybrid granular activated sludge system

Sludge granulation in continuous-flow systems is an emerging technology to intensify existing activated sludge infrastructure for nutrient removal. In these systems, the nutrient removal contributions and partitioning of microbial functions between granules and flocs can offer insights into process implementations. To this end, a reactor system that simulates the continuous-flow environment using an equal amount of initial granule and floc biomass was investigated. The two operational strategies for maintaining granule growth in the continuous-flow system were (a) the higher solids retention time (SRT) for the granules versus flocs, as well as (b) selective feeding of carbon to the granules. The SRT of the large granule fractions (>425 µm, LG) and floc/small granule fractions (<425 µm, FSG) were controlled at 20 and 2.7-6.0 days, respectively. Long term operation of the hybrid granule/floc system achieved high PO₄^3- and NH₄⁺ removal efficiencies. Higher polyphosphate-accumulating organisms (PAO) activity was observed in the FSG than LG, while ammonia-oxidizing bacteria (AOB) activities were similar in the two biomass fractions. Nitrite shunt was observed in the FSG, possibly due to out-competition by the high NOB activity in LG. More importantly, washing out the FSG caused a reduction in LG's AOB and PAO activity, indicating a possible dependency of LG on FSG for maintaining its nutrient removal capacity. Our findings highlighted the partitioning and potential competition/cooperation of key microbial functional groups between LG and FSG, facilitating nutrient removal in a hybrid granular activated sludge system, as well as implications for practical application of the treatment platform.

A Simple Culture Method Enhances the Recovery of Culturable Actinobacteria From Coastal Sediments

Molecular methods revealed that the majority of microbes in natural environments remains uncultivated. To fully understand the physiological and metabolic characteristics of microbes, however, culturing is still critical for microbial studies. Here, we used bacterial community analysis and four culture media, namely, traditional marine broth 2216 (MB), water extracted matter (WEM), methanol extracted matter (MEM), and starch casein agar (SCA), to investigate the diversity of cultivated bacteria in coastal sediments. A total of 1,036 isolates were obtained in pure culture, and they were classified into five groups, namely, Alphaproteobacteria (52.51%), Gammaproteobacteria (23.26%), Actinobacteria (13.32%), Firmicutes, and Bacteroidetes. Compared to other three media, WEM recovered a high diversity of actinobacteria (42 of 63 genotypes), with Micromonospora and Streptomyces as the most cultivated genera. Amplicon sequencing of the bacterial 16S ribosomal RNA (rRNA) gene V3-V4 fragment revealed eight dominant groups, Alphaproteobacteria (12.81%), Gammaproteobacteria (20.07%), Deltaproteobacteria (12.95%), Chloroflexi (13.09%), Bacteroidetes (8.28%), Actinobacteria (7.34%), Cyanobacteria (6.20%), and Acidobacteria (5.71%). The dominant members affiliated to Actinobacteria belonged to "Candidatus Actinomarinales," "Candidatus Microtrichales," and Nitriliruptorales. The cultivated actinobacteria accounted for a small proportion (<5%) compared to the actinobacterial community, which supported that the majority of actinobacteria are still waiting for cultivation. Our study concluded that WEM could be a useful and simple culture medium that enhanced the recovery of culturable actinobacteria from coastal sediments.

Proposal for transfer of Defluviimonas alba to the genus Frigidibacter as Frigidibacter mobilis nom. nov

A polyphasic taxonomic study was undertaken to clarify the exact position of the type strain cai42^T of the species Defluviimonas alba Pan et al. 2015. The results of the 16S rRNA gene sequence analysis indicated that the two sequences from cai42^T shared 99.6 and 99.7 % similarity to that of the type strain SP32^T of the species Frigidibacter albus and formed a coherent clade in the phylogenetic tree. Whole genomic comparison between cai42^T and SP32^T yielded a digital DNA-DNA hybridization estimate of 36.3 %, an average nucleotide identity of 88.8 % and an average amino acid identity of 89.8 %, clearly indicating that the two strains should belong to two genospecies of the same genus. The close relationship between the two strains was underpinned by the results of genome-based phylogenetic analysis. Although cai42^T and SP32^T shared similar physiological and biochemical properties, some striking differences, such as mobility, the temperature range for growth and the polar lipid components, could distinguish them as separate species. Therefore, the comparative phenotypic and genotypic analyses supported the incorporation of Defluviimonas alba into the genus Frigidibacter as Frigidibacter mobilis nom. nov. with the type strain cai42^T (=CGMCC 1.12518^T=LMG 27406^T).

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.

Application of a novel two-stage biofiltration system for simulated brackish aquaculture wastewater treatment

Biofiltration is one kind of common technology used for treating micro-polluted brackish aquaculture wastewater. Based on the characteristics of actual water quality, a novel two-stage biofiltration system was set up to reduce potential nutrient pollution brought by the frequent exchange of water in brackish pond aquaculture. Zeolite was selected as filtration media for the first stage and pyrite mixed with a small amount of sulfur for the second stage. Apart from the adsorption of nutrients exerted by these natural minerals, biofilm played a leading role in nutrient removal. The surface and internal pore of zeolite-sheltered nitrifiers and sulfur-containing compounds enhanced autotrophic denitrification. It was found that ammonia adsorption capacity of zeolite was reduced by nearly 58% when salinity was increased to 1.5%, while phosphate adsorption capacity of pyrite was hardly influenced and systematic hydraulic retention time (HRT) of 24 h was proven appropriate, 9.6 h and 14.4 h for the two stages, respectively. Meanwhile, removal efficiency of 96.5% for NH₄⁺-N and 92.1% for total inorganic nitrogen (TIN) was achieved under this condition. The analysis of microbial community of biofilm indicated that dominant genera responsible for nitritation and nitration on the surface of zeolite were Nitrosomonas and Nitrospira, respectively. Dominant genera responsible for autotrophic denitrification on the surface of pyrite and sulfur were both Thiobacillus. In addition, Ferritrophicum, related to the iron-oxidizing bacterium, also coexisted due to biological oxidation of pyrite. Long-term operation verified applicability and stability of this two-stage biofiltration system for brackish aquaculture wastewater purification.

Defluviimonas alba sp. nov., isolated from an oilfield

Two Gram-stain-negative, rod-shaped bacterial strains, cai42T and b45, were isolated from oil-production water taken from Xinjiang Oilfield, China. Optimum growth was observed at 30 °C, at pH 8 and with 1–3 % (w/v) NaCl. According to phylogenetic analyses, the two strains were members of the genus Defluviimonas , with 16S rRNA gene sequence similarities of 95.5−96.3 % with the type strains of species of the genus. The major cellular fatty acids of strains cai42T and b45 were C10 : 0 3-OH, C16 : 0 and summed feature 8 (C18 : 1ω7c/C18 : 1ω6c), and the predominant ubiquinone was Q-10, all of these data being typical for the genus Defluviimonas . The polar lipids were phosphatidylethanolamine, phosphatidylglycerol, glycolipid, phosphatidylcholine, two unidentified aminolipids, an unidentified phospholipid and two unidentified lipids. The mean genomic DNA G+C contents of strains cai42T and b45 were 60.8±1.1 and 60.4±1.0 mol%, respectively. On the basis of phylogenetic, physiological and chemotaxonomic analyses, strains cai42T and b45 represent a novel species of the genus Defluviimonas , for which the name Defluviimonas alba sp. nov. is proposed. The type strain is cai42T ( = CGMCC 1.12518T = LMG 27406T).

Frigidibacter albus gen. nov., sp. nov., a novel member of the family Rhodobacteraceae isolated from lake water

Three Gram-staining-negative, strictly aerobic, non-pigmented, non-motile, rod-shaped bacterial strains, SP32T ( = SLM-1T), SR68 ( = SLM-3) and SP95 ( = SLM-2), were isolated from two water samples of a cold-water lake in Xinjiang province, China. Growth was observed at 4–25 °C and pH 6.0–9.0, and optimum growth occurred at 18–20 °C and at pH 7.0–7.5. Phylogenetic analysis of 16S rRNA gene sequences revealed that these isolates belonged to the family Rhodobacteraceae , but formed an evolutionary lineage distinct from other species of this family with validly published names. Strain SP32T showed the highest 16S rRNA gene sequence similarity (96.7 %) to Rhodobacter veldkampii ATCC 35703T, and the similarity to members of the genera Defluviimonas , Haematobacter and Pseudorhodobacter was respectively 95.8–96.4, 96.0–96.1 and 95.3–96.1 %. The genomic DNA G+C content of strain SP32T was 67.6 mol%. The major fatty acids (>5 %) were summed feature 8 (C18 : 1ω7c/C18 : 1ω6c) and11-methyl C18 : 1ω7c. Phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol, phosphatidylcholine, one unidentified glycolipid and one unidentified polar lipid were the main polar lipids. Ubiquinone 10 (Q-10) was the sole respiratory quinone. Strain SP32T did not produce photosynthetic pigments and did not contain the gene pufM, by which it differed from the phototrophic species of the family Rhodobacteraceae . Based on its distinct phenotypic, chemotaxonomic and phylogenetic properties, strain SP32T represents a novel species in a novel genus within the family Rhodobacteraceae , for which we propose the name Frigidibacter albus gen. nov., sp. nov. The type strain of Frigidibacter albus is strain SP32T ( = SLM-1T = CGMCC 1.13995T = NBRC 109671T).

Defluviimonas aquaemixtae sp. nov., isolated from the junction between a freshwater spring and the ocean

A Gram-stain-negative, coccoid- or short-rod-shaped and non-gliding bacterial strain, designated CDM-7T, was isolated from the zone where the ocean meets a freshwater spring at Jeju island, South Korea, and was subjected to a polyphasic taxonomic study. Strain CDM-7T grew optimally at pH 7.0–8.0, at 30 °C and in the presence of 2–3 % (w/v) NaCl. Neighbour-joining, maximum-likelihood and maximum-parsimony phylogenetic trees based on 16S rRNA gene sequences showed that strain CDM-7T falls within the clade comprising species of the genus Defluviimonas, clustering with the type strain of Defluviimonas aestuarii , with which it exhibited the highest 16S rRNA gene sequence similarity value (98.4 %). The 16S rRNA gene sequence similarity values between strain CDM-7T and the type strains of Defluviimonas denitrificans and Defluviimonas indica were 97.1 and 96.2 %, respectively. The genomic DNA G+C content was 66.8 mol% and the mean DNA–DNA relatedness values between strain CDM-7T and the type strains of D. aestuarii and D. denitrificans were 15.6±2.5 and 6.7±3.2 %, respectively. Strain CDM-7T contained Q-10 as the predominant ubiquinone and summed feature 8 (C18 : 1ω7c and/or C18 : 1ω6c) as the major fatty acid. The major polar lipids were phosphatidylcholine, phosphatidylglycerol, an unidentified aminolipid, an unidentified phospholipid and an unidentified lipid. Differential phenotypic properties, together with the phylogenetic and genetic distinctiveness, demonstrated that strain CDM-7T is distinguishable from other species of the genus Defluviimonas . On the basis of the data presented, strain CDM-7T is considered to represent a novel species of the genus Defluviimonas , for which the name Defluviimonas aquaemixtae sp. nov. is proposed. The type strain is CDM-7T ( = KCTC 42108T = CECT 8626T).

Defluviimonas indica sp. nov., a marine bacterium isolated from a deep-sea hydrothermal vent environment

A Gram-stain-negative, strictly aerobic, chemoheterotrophic marine bacterium, designated 20V17T, was isolated from a deep-sea hydrothermal vent chimney collected from the South-west Indian Ridge. Cells of strain 20V17T were motile, short rods, 1.2–1.8 µm in length and 0.5–0.7 µm in width. Growth was observed at between 20 and 37 °C (optimum 25 °C–28 °C), pH 5.0 and 8.0 (optimum pH 7.0) and 0.5 and 8 % (w/v) NaCl (optimum 1.5–2.0 % NaCl). The major fatty acids were C18 : 1ω7c (74.4 %), C19 : 0 cyclo ω8c (11 %), C18 : 0 (5.1 %) and C18 : 0 3-OH (2.8 %), and the polar lipid profile comprised diphosphatidylglycerol, phosphatidylethanolamine, an unidentified glycolipid and four unidentified phospholipids. Ubiquinone 10 was the major quinone. The G+C content of genomic DNA was 66.3 mol%. Phylogenetic analyses based on 16S rRNA gene sequences showed that strain 20V17T belonged to the genus Defluviimonas and shared 96.5 and 96.1 % sequence similarity with Defluviimonas denitrificans D9-3T and Defluviimonas aestuarii BS14T, respectively. On the basis of the taxonomic data obtained in this study, strain 20V17T represents a novel species of the genus Defluviimonas , for which the name Defluviimonas indica sp. nov. is proposed. The type strain is 20V17T (CGMCC 1.10859T = JCM 17871T = MCCC 1A01802T).