Massilia litorea sp. nov., Marinobacter salinisoli sp. nov. and Rhodobacter xanthinilyticus sp. nov., isolated from coastal environments.

Three bacterial strains, namely LPB0304T, LPB0319T and LPB0142T, were isolated from coastal environments. The 16S rRNA gene sequences of the three isolates were found to show the highest sequence similarities to Massilia litorea (98.44 %), Marinobacter salinisoli (97.55 %) and Rhodobacter lacus (97.60 %), respectively. The low (<98.7 %) sequence similarities and tree topologies implied the novelty of the three isolates, representing novel genomic species of the genus Massilia, Marinobacter and Rhodobacter. Numerous biochemical and physiological features also supported the distinctiveness of the isolates from previously known species. Based on the phenotypic and phylogenetic data presented in this study, three novel species are suggested with the following names: Massilia litorea sp. nov. (LPB0304T=KACC 21523T=ATCC TSD-216T), Marinobacter salinisoli sp. nov. (LPB0319T=KACC 21522T=ATCC TSD-218T) and Rhodobacter xanthinilyticus sp. nov. (LPB0142T=KACC 18892T=JCM 31567T).

Genome sequence and characterisation of a freshwater photoarsenotroph, Cereibacter azotoformans strain ORIO, isolated from sediments capable of cyclic light-dark arsenic oxidation and reduction.

A freshwater photosynthetic arsenite-oxidizing bacterium, Cereibacter azotoformans strain ORIO, was isolated from Owens River, CA, USA. The waters from Owens River are elevated in arsenic and serve as the headwaters to the Los Angeles Aqueduct. The complete genome sequence of strain ORIO is 4.8 Mb genome (68% G + C content) and comprises two chromosomes and six plasmids. Taxonomic analysis placed ORIO within the Cereibacter genus (formerly Rhodobacter). The ORIO genome contains arxB2 AB1 CD (encoding an arsenite oxidase), arxXSR (regulators) and several ars arsenic resistance genes all co-localised on a 136 kb plasmid, named pORIO3. Phylogenetic analysis of ArxA, the molybdenum-containing arsenite oxidase catalytic subunit, demonstrated photoarsenotrophy is likely to occur within members of the Alphaproteobacteria. ORIO is a mixotroph, oxidises arsenite to arsenate (As(V)) photoheterotrophically, and expresses arxA in cultures grown with arsenite. Further ecophysiology studies with Owens River sediment demonstrated the interconversion of arsenite and As(V) was dependent on light-dark cycling. arxA and arrA (As(V) respiratory reductase) genes were detected in the light-dark cycled sediment metagenomes suggesting syntrophic interactions among arsenotrophs. This work establishes C. azotoformans str. ORIO as a new model organism for studying photoarsenotrophy and light-dark arsenic biogeochemical cycling.

Cereibacter flavus sp. nov., a novel member of the family Rhodobacteraceae isolated from seawater of the South China Sea and reclassification of Rhodobacter alkalitolerans as Cereibacter alkalitolerans comb. nov.

A Gram-stain-negative, aerobic, motile, ovoid-shaped and yellow-coloured strain, designated SYSU M79828T, was isolated from seawater collected from the South China Sea. Growth of this strain was observed at 4-37 °C (optimum, 28 °C), pH 6.0-8.0 (optimum, pH 7.0) and with 0-6% NaCl (optimum, 3.0 %, w/v). The respiratory quinone was found to be Q-10. Major fatty acid constituents were C18 : 1 ω7c/C18 : 1 ω6c, C18 : 1 ω7c11-methyl and C18 : 0 (>5 % of total). The major polar lipids were phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol, phosphatidylcholine, phosphoglycolipid, two unidentified phospholipid, one unidentified lipid and an unidentified glycolipid. The genomic DNA G+C content was 64.5 mol%. Phylogenetic analyses based on 16S rRNA gene sequences and core genes indicated that strain SYSU M79828T belonged to the genus Cereibacter and had the highest sequences similarity to 'Rhodobacter xinxiangensis' TJ48T (98.41 %). Based on 16S rRNA gene phylogeny, physiological and chemotaxonomic characterizations, we consider that strain SYSU M79828T represents a novel species of the genus Cereibacter, for which the name Cereibacter flavus sp. nov. is proposed. The type strain is SYSU M79828T (=GDMCC 1.3803T=KCTC 92893T). In addition, according to the results of phylogenetic analysis and similar taxonomic characteristics, we propose that Rhodobacter alkalitolerans should be reclassified as Cereibacter alkalitolerans comb. nov.

Anoxygenic phototrophic arsenite oxidation by a Rhodobacter strain.

Microbially mediated arsenic redox transformations are key for arsenic speciation and mobility in rice paddies. Whereas anaerobic anoxygenic photosynthesis coupled to arsenite (As(III)) oxidation has been widely examined in arsenic-replete ecosystems, it remains unknown whether this light-dependent process exists in paddy soils. Here, we isolated a phototrophic purple bacteria, Rhodobacter strain CZR27, from an arsenic-contaminated paddy soil and demonstrated its capacity to oxidize As(III) to arsenate (As(V)) using malate as a carbon source photosynthetically. Genome sequencing revealed an As(III)-oxidizing gene cluster (aioXSRBA) encoding an As(III) oxidase. Functional analyses showed that As(III) oxidation under anoxic phototrophic conditions correlated with transcription of the large subunit of the As(III) oxidase aioA gene. Furthermore, the non-As(III) oxidizer Rhodobacter capsulatus SB1003 heterologously expressing aioBA from strain CZR27 was able to oxidize As(III), indicating that aioBA was responsible for the observed As(III) oxidation in strain CZR27. Our study provides evidence for the presence of anaerobic photosynthesis-coupled As(III) oxidation in paddy soils, highlighting the importance of light-dependent, microbe-mediated arsenic redox changes in paddy arsenic biogeochemistry.

A novel strategy to improving Rhodobacter azotoformans denitrification efficiency: Insight into the role of a two-component system NtrX/Y in denitrification regulation.

Transcription factors (TFs) can manage the coordinated expression of genes clusters or multiple genes. TF was used to improve bacterial denitrification ability in this study. During denitrification, the ntrY of R. azotoformans, which encodes the sensor of NtrX/Y system, was significantly upregulated in transcription. Denitrification of the mutant △ntrY was significantly inhibited, and it was recovered after replenishing this gene to the mutant, which indicates the NtrX/Y system plays an important role in regulating bacterial denitrification. According to additional research, the NtrX/Y system regulates bacterial denitrification by directly promoting the expression of the nitrite reductase. ntrY overexpression appears to accelerate bacterial denitrification, and the introduction of a strong promoter tac in conjunction with iron supply optimization increases the rate by 72% further. This study realizes bacterial denitrification enhancement from the perspective of global transcription regulation, which provides a novel strategy for improving microbial ability to degrade pollutants.

Safety assessment of Rhodobacter azotoformans SY5 for potential application in Chinese mitten crab Eriocheir sinensis.

Rhodobacter species are promising beneficial microbes that can improve growth performance, immunity and antioxidant capability in aquatic crustaceans. Yet the safety of Rhodobacter azotoformans for potential application in Chinese mitten crab Eriocheir sinensis is still unclear. In the present study, R. azotoformans SY5, a potential probiotic additive that can significantly improve the growth performance, immunity, antioxidant capability, and disease resistance in E. sinensis, was evaluated for safety through whole genome sequencing, antibiotic resistance, toxic metabolites, virulence, and crab tolerance assays. The results indicated that R. azotoformans SY5 only harboured the acyl carrier protein-encoding gene (acpP) that was universal in probiotic bacteria with the function of bacterial fatty acid biosynthesis, exhibited high susceptibility to aminoglycosides, penicillins, polymyxins, polyphosphates, quinolones, and tetracyclines antimicrobials, and possessed inability to produce hemolysin, hydrogen sulphide, nitrite, ammonia, and phenylpyruvate. In addition, R. azotoformans SY5 showed no pathogenicity for E. sinensis with the seven-day acute intraperitoneal LD50 value of above 6.0 × 109 cfu/ml and 30-day chronic oral LD50 of above 6.0 × 109 cfu/g diet. To our knowledge, this is the first report on the safety of R. azotoformans for potential application in Chinese mitten crabs.

Rhodobacter azotoformans supplementation improves defense ability of Chinese mitten crab Eriocheir sinensis against citrobacteriosis.

Rhodobacter probiotics are considered as good alternatives to antibiotics for aquaculture. Yet the beneficial effects of Rhodobacter on Chinese mitten crab Eriocheir sinensis are still unclear, and more functions of Rhodobacter supplementation need to be clarified. In this study, a 60-day feeding trial was performed to investigate the protective effects of R. azotoformans against citrobacteriosis in E. sinensis by growth performance, serum immunity, hepatopancreatic antioxidant capability, intestinal flora, and resistance to Citrobacter freundii challenge assays. The results showed that R. azotoformans supplementation significantly and dose-dependently increased weight gain and specific growth rate as well as activities of serum immune and hepatopancreatic antioxidant enzymes, leading to notable improvement in the growth performance, serum immunity and hepatopancreatic antioxidant status of E. sinensis. Besides, R. azotoformans supplementation significantly enhanced intestinal microbial abundance and diversity in E. sinensis, and conferred significant protection of the crabs against C. freundii challenge with seven-day survival rates of 70.0%-100.0%. To the best of our knowledge, this is the first study to reveal the protective effects of R. azotoformans against citrobacteriosis in E. sinensis.

Lipopolysaccharide from Rhodobacter spheroids modulate toll-like receptors expression and tissue damage in an animal model of bilateral renal ischemic reperfusion injury.

Ischemic reperfusion injury (IRI) of the kidneys is a direct sequela of surgical procedures associated with the interruption of blood supply. The pathophysiology of IRI is complicated, and several inflammatories, apoptosis, and oxidative stress pathways are implicated. Among the major receptors directly involved in renal IRI are the toll-like receptors (TLRs), specifically TLR2 and TLR4. In this study, we investigated the effects of Lipopolysaccharide from Rhodobacter Sphaeroides (TLR2 and TLR4 antagonist, LPS-RS) and the ultrapure form (pure TLR4 antagonist, ULPS-RS) on the histopathological changes and TLRs expression in an animal model of bilateral renal IRI. Forty-eight adult male rats were allocated into six groups (N=8) as follows: sham group (negative control without IRI), control group (rats underwent bilateral renal ischemia for 30 minutes and 2 hours of reperfusion), vehicle group (IRI+ vehicle), LPS-RS group (IRI+ 0.5 mg/kg of LPS-RS), ULPS-RS group (IRI+ 0.1 mg/kg of ULPS-RS), ULPS-RSH group (IRI+ 0.2 mg/kg of ULPS-RS). Significant improvement in the histopathological damages induced by renal IRI was found in the ULPS-RS treated groups at both doses compared with the control group. The protective effect of ULPS-RS was associated with significantly reduced TLR4 expression without affecting TLR2. Regarding LPS-RS, the tested dose adversely affected the renal tissues as manifested by the histopathological findings, although it similarly affected TLRs expression as ULPS-RS. Our results demonstrated that ULPS-RS was renoprotective while LPS-RS had no protective effect against the tissue damages induced by renal IRI.

Ammonia assimilation: A double-edged sword influencing denitrification of Rhodobacter azotoformans and for nitrogen removal of aquaculture wastewater.

NO3--N and NH4+-N are two prevalent nitrogenous pollutants in aquaculture wastewater posing a significant health risk to aquatic animals. R. azotoformans ATCC17025 can rapidly denitrify to remove NO3--N, assimilating NH4+-N. The study investigated the influence of ammonia assimilation on bacterial denitrification. Results revealed that low concentration of NH4+-N (≤0.3 mM) accelerated denitrification, whereas high concentration inhibited it. RT-qPCR indicated that the inhibition of NO reduction under high concentration of NH4+-N was the primary cause of denitrification depression, whereas low concentration of NH4+-N enhanced the synthesis of practically all enzymes involved in denitrification. Finally, nitrogen-rich aquaculture effluent was effectively treated in lab-scale using a semi-continuous operation that provided an appropriate NH4+-N concentration for denitrification. This semi-continuous operation treated wastewater 2 times faster than the batch operation and the content of nitrogen decreased to effluent standard. The study can provide guidance for nitrogen removal of aquaculture wastewater with bioaugmentation.

Influence of blue light on effective removal of arsenic by photosynthetic bacterium Rhodobacter sp. BT18.

Arsenic (As) contamination in an ecosystem has been a serious threat for the ecosystem as well as human health. Thus, the present study was established an eco-friendly remediation of As by using As resistant Rhodobacter sp. Accordingly, the growth of Rhodobacter sp. in As stress environment was assessed. Expectedly, enhanced growth order of the Rhodobacter sp., under As stress was found to be control >50 > 100 > 200 > 300 > 400 > 500 mg/L of As. In addition, the present study explored the influence of various light sources (Yellow, light blue, red, green and white) on growth and As removal mechanisms of Rhodobacter sp. The growth profile of the bacteria indicated that the light blue source showed an enhanced growth at 72 h of incubation. Based on optimization experiments, an increased As removal percentage rate was found to be at 87.5% at pH 7.0, 3% of glucose, 1% of citrate supplemented in the medium. The As resistant genetic pattern for arsenic transformation, the genes arsenate reductase (arsC), arsenite oxidase (aio) was investigated. To study the transcript level expression of arsC and aio genes were performed after exposure to different concentrations of As (50, 100, 150, and 200 mg/L) at different time intervals (24, 48, 72 and 96 h). The results showed that both arsC and aio were up regulated from 24 to 72 h and the down regulation was observed at 96 h. The obtained results indicated that the Rhodobacter sp., possess significant AS tolerance and removal potential would make it is a noteworthy candidate for future As remediation practices.

Rhodobacter amnigenus sp. nov. and Rhodobacter ruber sp. nov., isolated from freshwater habitats.

Two bacterial strains, designated HSP-20T and CCP-1T, isolated from freshwater habitats in Taiwan, were characterized by polyphasic taxonomy. Both strains were Gram-stain-negative, aerobic, non-motile and rod-shaped. Cells of strains HSP-20T and CCP-1T formed pink and dark red coloured colonies, respectively. Both strains contained bacteriochlorophyll a, and showed optimum growth under anaerobic conditions by photoheterotrophy, but no growth by photoautotrophy. Phylogenetic analyses based on 16S rRNA gene and whole-genome sequences indicated that both strains belonged to the genus Rhodobacter. Analysis of 16S rRNA gene sequences showed that strains HSP-20T and CCP-1T shared 98.3 % sequence similarity and were closely related to Rhodobacter tardus CYK-10T (96.0 %) and Rhodobacter flagellatus SYSU G03088T (96.0 %), respectively. Both strains shared common chemotaxonomic characteristics including Q-10 as the major isoprenoid quinone, C18 : 1 ω7c as the predominant fatty acid, and phosphatidylethanolamine, phosphatidylglycerol and phosphatidylcholine as the main polar lipids. The DNA G+C content of both strains was 66.2 mol%. The average nucleotide identity, average amino acid identity and digital DNA-DNA hybridization values between these two novel isolates and their closest relatives were below the cut-off values of 95-96, 90 and 70 %, respectively, used for species demarcation. On the basis of phenotypic and genotypic properties and phylogenetic inference, both strains should be classified as novel species within the genus Rhodobacter, for which the names Rhodobacter amnigenus sp. nov. (=BCRC 81193T=LMG 31334T) and Rhodobacter ruber sp. nov. (=BCRC 81189T=LMG 31335T) are proposed.

Rhodobacter kunshanensis sp. nov., a Novel Bacterium Isolated from Activated Sludge.

Strain HX-7-19T was isolated from the activated sludge collected from an abandoned herbicide manufacturing plant in Kunshan, China. Cells were Gram-reaction-negative, rod-shaped, and non-motile. The phylogenetic analysis based on 16S rRNA gene indicated that strain HX-7-19T formed a clade with Rhodobacter blasticus CGMCC 1.3365T (96.3% sequence similarity). The average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values between strain HX-7-19T and R. blasticus CGMCC 1.3365T were 76.2% and 20.3%, respectively. The genomic DNA G + C content of strain HX-7-19T was 65.9%. The major fatty acids (> 10% of the total fatty acids) were C18:1 ω7c and C18:1 ω7c 11-methyl. The major respiratory quinone was quinone Q-10. The major polar lipid profile consists of phosphatidylglycerol (PG), diphosphatidyl-glycerol (DPG), phosphatidylethanolamine (PE), and phosphatidylcholine (PC). Photosynthesis pigments bacteriochlorophyll a and carotenoids were formed and photosynthesis genes pufL and pufM were detected. On the basis of phenotypic and phylogenetic evidences, strain HX-7-19T is considered as a novel species in the genus Rhodobacter, for which the name Rhodobacter kunshanensis sp. nov. is proposed. The type strain is HX-7-19T (= KCTC 72471T = CCTCC AB 2020148T).

Rhodobacter azotoformans LPS (RAP99-LPS) Is a TLR4 Agonist That Inhibits Lung Metastasis and Enhances TLR3-Mediated Chemokine Expression.

The lipopolysaccharides (LPSs) of Rhodobacter are reported to be TLR4 antagonists. Accordingly, the extract of Rhodobacter azotoformans (RAP99) is used as a health supplement for humans and animals in Japan to regulate immune responses in vivo. We previously analyzed the LPS structure of RAP99 (RAP99-LPS) and found it is different from that of E. coli-LPS but similar to lipid A from Rhodobacter sphaeroides (RSLA), a known antagonist of TLR4, with both having three C14 fatty acyl groups, two C10 fatty acyl groups, and two phosphates. Here we show that RAP99-LPS has an immune stimulatory activity and acts as a TLR4 agonist. Pretreatment of RAP99-LPS suppressed E. coli-LPS-mediated weight loss, suggesting it is an antagonist against E. coli-LPS like other LPS isolated from Rhodobacter. However, injections of RAP99-LPS caused splenomegaly and increased immune cell numbers in C57BL/6 mice but not in C3H/HeJ mice, suggesting that RAP99-LPS stimulates immune cells via TLR4. Consistently, RAP99-LPS suppressed the lung metastasis of B16F1 tumor cells and enhanced the expression of TLR3-mediated chemokines. These results suggest that RAP99-LPS is a TLR4 agonist that enhances the activation status of the immune system to promote anti-viral and anti-tumor activity in vivo.

Cocultivating aerobic heterotrophs and purple bacteria for microbial protein in sequential photo- and chemotrophic reactors.

Aerobic heterotrophic bacteria (AHB) and purple non-sulfur bacteria (PNSB) are typically explored as two separate types of microbial protein, yet their properties as respectively a bulk and added-value feed ingredient make them appealing for combined use. The feasibility of cocultivation in a sequential photo- and chemotrophic approach was investigated. First, mapping the chemotrophic growth kinetics for four Rhodobacter, Rhodopseudomonas and Rhodospirillum species on different carbon sources showed a preference for fructose (µmax 2.4-3.9 d-1 28 °C; protein 36-59%DW). Secondly, a continuous photobioreactor inoculated with Rhodobacter capsulatus (VFA as C-source) delivered the starter culture for an aerobic batch reactor (fructose as C-source). This two-stage system showed an improved nutritional quality compared to AHB production: higher protein content (45-71%DW), more attractive amino/fatty acid profile and contained up to 10% PNSB. The findings strengthen protein production with cocultures and might enable the implementation of the technology for resource recovery on streams such as wastewater.

Dysbiosis of the endometrial microbiota and its association with inflammatory cytokines in endometrial cancer.

The underlying molecular mechanisms involved in the pathogenesis of endometrial cancer (EC) are still not well understood. Our goal was to investigate the composition of the endometrial microbiota and the association with inflammatory cytokines in EC. Endometrial microbiota profiles of women with EC (n = 25) and benign uterine lesions (BUL, n = 25) were assessed by 16S ribosomal RNA gene amplicon sequencing. The expression levels of interleukin-6 (IL-6), interleukin-8 (IL-8), and interleukin-17 (IL-17) mRNA and protein in the endometrial tissues of the two groups were determined by real-time quantitative polymerase chain reaction and Western blot, respectively. There were significant differences in alpha diversity based on the observed operational taxonomic units (P = .002), Pielou evenness (P = .001), and Shannon index (P < .001) between EC and BUL groups. Significant differences were also found in Bray-Curtis (P = .001) and unweighted UniFrac (P = .001) beta diversity measures between the two groups. At the genus level, Micrococcus was more abundant in the EC group. Pseudoramibacter_Eubacterium, Rhodobacter, Vogesella, Bilophila, Rheinheimera, and Megamonas were enriched in the BUL group. There were no differences in IL-8 and IL-17 protein levels between the two groups, except IL-6 protein levels. However, the mRNA expression levels of IL-6, IL-8, and IL-17 were significantly different. Moreover, the relative abundances of Micrococcus was positively correlated with IL-6, and IL-17 mRNA levels. In conclusion, our results suggested that dysbiosis of endometrial microbiota and the inflammatory cytokines were associated with Micrococcus in EC patients, which might be useful for exploration of the mechanism between the endometrial microbiota and inflammatory responses in future studies.

Effects of glycine on cell growth and pigment biosynthesis in Rhodobacter azotoformans.

The effect of exogenous glycine (a precursor for the biosynthesis of bacteriochlorophyll) on the cell growth and photopigment accumulation was investigated in phototrophic growing Rhodobacter azotoformans 134K20. The growth rate and the biomass of strain 134K20 were significantly inhibited by glycine addition when ammonium sulfate or glutamate were used as nitrogen sources and acetate or succinate as carbon sources. A characteristic absorption maximum at approximately 423 nm was present in the absorption spectra of glutamate cultures while it was absent by the addition of high-concentration glycine of 15 mM. The component account for the 423 nm peak was eventually identified as magnesium protoporphyrin IX monomethyl ester, a precursor of bacteriochlorophyll a (BChl a). Comparative analysis of pigment composition revealed that the amount of BChl a precursors was significantly decreased by the addition of 15-mM glycine while the BChl a accumulation was increased. Moreover, glycine changed the carotenoid compositions and stimulated the accumulation of spheroidene. The A850 /A875 in the growth-inhibited cultures was increased, indicating an increased level of the light-harvesting complex 2 compared to the reaction center. The exogenous glycine possibly played an important regulation role in photosynthesis of purple bacteria.

Tabrizicola oligotrophica sp. nov. and Rhodobacter tardus sp. nov., two new species of bacteria belonging to the family Rhodobacteraceae.

Two Gram-stain-negative, aerobic, non-motile bacteria, designated KMS-5T and CYK-10T, were isolated from freshwater environments. 16S rRNA gene sequence similarity results indicated that these two novel strains belong to the family Rhodobacteraceae. Strain KMS-5T is closely related to species within the genus Tabrizicola (96.1-96.8 % sequence similarity) and Cypionkella (96.5-97.0 %). Strain CYK-10T is closest to Rhodobacter thermarum YIM 73036T with 96.6 % sequence similarity. Phylogenetic analyses based on 16S rRNA gene sequences and an up-to-date bacterial core gene set showed that strain KMS-5T is affiliated with species in the genus Tabrizicola and strain CYK-10T is placed in a distinct clade with Rhodobacter blasticus ATCC 33485T, Rhodobacter thermarum YIM 73036T and Rhodobacter flagellatus SYSU G03088T. These two strains shared common chemotaxonomic features comprising Q-10 as the major quinone, phosphatidylethanolamine, phosphatidylglycerol and phosphatidylcholine as the principal polar lipids, and C18 : 1 ω7c as the main fatty acid. The average nucleotide identity, average amino acid identity and digital DNA-DNA hybridization values between these two novel isolates and their closest relatives were below the cut-off values of 95-96, 90 and 70 %, respectively, used for species demarcation. The obtained polyphasic taxonomic data suggested that strain KMS-5T represents a novel species within the genus Tabrizicola, for which the name Tabrizicola oligotrophica sp. nov. is proposed with KMS-5T (=BCRC 81196T=LMG 31337T) as the type strain, and strain CYK-10T should represent a novel species of the genus Rhodobacter, for which the name Rhodobacter tardus sp. nov. is proposed with CYK-10T (=BCRC 81191T=LMG 31336T) as the type strain.

"Sporotan" a new fluorescent stain for identifying cryptic spores of Rhodobacter johrii.

We propose a new fluorescent stain "sporotan" and staining protocol which aid in the identification of cryptic endospores which are otherwise mistaken as poly-ß-hydroxyalkanoate granules.

Mixed-culture aerobic anoxygenic photosynthetic bacterial consortia reduce nitrate: Core species dynamics, co-interactions and assessment in raw water of reservoirs.

Three consortia of mixed-culture Aerobic Anoxygenic Photosynthetic Bacteria (AAPB) with excellent aerobic denitrifying ability were isolated from drinking water source reservoirs. The results showed that the removal of dissolved organic carbon (DOC) and nitrate nitrogen (NO3--N) by mixed-culture AAPB were higher than 90% and 99%, respectively. The Illumina MiSeq sequencing of pufM gene revealed that the dominant genera and their relative abundance changed over the culture periods. Sphingomonas sanxanigenens was the most dominant species observed at 9 h, whereas at 48 h, the most abundant species was Rhodobacter blasticus. A network analysis demonstrated that the co-interactions among the different genera were complex and variable. Mixed-culture AAPB removed more than 30% of NO3--N and 25% of DOC from the source water and this study suggests that mixed-culture AAPB can be regarded as a latent denitrifying microbial inoculum in the reservoir raw water treatment.

Rhodobacter xinxiangensis sp. nov., isolated from pakchoi-cultivated soil contaminated with heavy metal and its potential to reduce Cd and Pb accumulation in pakchoi (Brassica campestris L.).

A Gram-stain-negative, aerobic, and motile strain, TJ48T, was isolated from pakchoi-cultivated soil contaminated with Cd and Pb in Xinxiang (China). Cells of the strain were rod-shaped and colonies on LB agar were faint yellow. Strain TJ48T was positive for catalase and oxidase and the optimal condition for growth was 28 °C, with 1% (w/v) NaCl and at pH 7.0. Phylogenetic analysis based on the 16S rRNA gene sequences showed that strain TJ48T was closely related to the genus Rhodobacter and the closest relatives were Rhodobacter ovatus JA234T (97.4%, 16S rRNA gene sequence similarity) and Rhodobacter azotoformans KA25T (96.5%). The DNA G + C content of strain TJ48T was 64.7 mol%. Genome-to-genome distance calculations (GGDC) and ANIb values from genomic comparison between the genomes of strain TJ48T and the related reference species were less than 70% and 95%, respectively. The major cellular fatty acids were summed feature 8 (C18:1ω7c and/or C18:1ω6c) and C17:0. The only isoprenoid quinone detected was Ubiquinone-10 (Q-10). The polar lipid profile contains diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, one unidentified aminophospholipid, one unidentified phospholipids, and three unidentified lipids. Strain TJ48T significantly increased the dry weight of roots (26.2-66.3%) and shoots (16.7-37.8%) of pakchoi and reduced the Cd (50.2-60.1%) and Pb (55.6-60.9%) contents in pakchoi shoots and roots. On the basis of the physiological, genotypic and genomic characteristics, the strain TJ48T represent a novel species of the genus Rhodobacter, and the name Rhodobacter xinxiangensis sp. nov. is proposed (type strain TJ48T = CCTCC AB2019120T = KCTC 72510T).