Groundwater denitrification using electro-assisted autotrophic processes: exploring bacterial community dynamics in a single-chamber reactor

Nitrate, a major groundwater pollutant from anthropogenic activities, poses serious health risks when present in drinking water. Denitrification using bio-electrochemical reactors (BER) offers an innovative technology, eco-friendly solution for nitrate removal from groundwater. BER use electroactive bacteria to reduce inorganic compounds like nitrate and bicarbonate by transferring electrons directly from the cathode. In our work, two batch BER were implemented at 1V and 2V, using anaerobic digestate from a full-scale wastewater treatment plant as inoculum. Nitrate, nitrite, sulfate, total ammoniacal nitrogen, and 16S rRNA analysis of bacterial community, were monitored during BER operation. The results showed effective nitrate removal in all BERs, with denitrification rate at 1V and 2V higher than the Control system, where endogenous respiration drove the process. At 1V, complete nitrate conversion to N2 occurred in 4 days, while at 2V, it took 14 days. The slower rate at 2V was likely due to O2 production from water electrolysis, which competed with nitrate as final electron acceptor. Bacterial community analysis confirmed the electroactive bacteria selection like the genus Desulfosporosinus and Leptolinea, confirming electrons transfer without an electroactive biofilm. Besides, Hydrogenophaga was enhanced at 2V likely due to electrolytically produced H2. Sulfate was not reduced, and total ammoniacal nitrogen remained constant indicating no dissimilatory nitrite reduction of ammonia. These results provide a significant contribution to the scaling up of electro-assisted autotrophic denitrification and its application in groundwater remediation, utilizing a simple reactor configuration-a single-chamber, membrane-free design- and a conventional power source instead of a potentiostat.

Rheinheimera oceanensis sp. nov., a novel member of the genus Rheinheimera, isolated from the West Pacific Ocean

Two Gram-stain-negative, aerobic, non-motile and short-rod-shaped bacteria, designated as strains GL-53T and GL-15-2-5, were isolated from the seamount area of the West Pacific Ocean and identified using a polyphasic taxonomic approach. The growth of strains GL-53ᵀ and GL-15-2-5 occurred at pH 5.5-10.0, 4-40 °C (optimum at 28 °C) and 0-10.0 % NaCl concentrations (optimum at 0-5.0 %). On the basis of 16S rRNA gene sequence analysis, strains GL-53ᵀ and GL-15-2-5 exhibited the highest similarity to Rheinheimera lutimaris YQF-2T (98.4 %), followed by Rheinheimera pacifica KMM 1406T (98.1 %), Rheinheimera nanhaiensis E407-8T (97.4 %), Rheinheimera aestuarii H29T (97.4 %), Rheinheimera hassiensis E48T (97.2 %) and Rheinheimera aquimaris SW-353T (97.2 %). Phylogenetic analysis revealed that the isolates were affiliated with the genus Rheinheimera and represented an independent lineage. The major fatty acids were summed feature 3 (C16 : 1  ω7c and/or C16 : 1  ω6c), C16 : 0 and summed feature 8 (C18 : 1  ω7c and/or C18 : 1  ω6c). The sole isoprenoid quinone was ubiquinone 8. The major polar lipids were phosphatidylethanolamine, phosphatidylglycerol, one unidentified aminophospholipid (and one unidentified glycolipid. The DNA G+C content was 48.5 mol%. The average nucleotide identity, average amino acid identity and in silico DNA-DNA hybridization values among the genomes of strain GL-53ᵀ and the related strains in the genus Rheinheimera were 75.5-90.1 %, 67.5-93.9 % and 21.4-41.4 %, respectively. Based on their phenotypic, chemotaxonomic and genotypic properties, the two strains were identified as representing a novel species of the genus Rheinheimera, for which the name Rheinheimera oceanensis sp. nov. is proposed. The type strain is GL-53T (=KCTC 82651T=MCCC M20598T).

Mercury remediation potential of mercury-resistant strain Rheinheimera metallidurans sp. nov. isolated from a municipal waste dumping site

A novel mercury-resistant bacterium, designated strain DCL_24^T, was isolated from the legacy waste at the Daddu Majra dumping site in Chandigarh, India. It showed resistance up to 300 µM of inorganic mercury (mercuric chloride). The isolate was found to be a Gram-negative, facultative anaerobic, motile, and rod-shaped bacterium that can grow at 4 - 30 °C (optimum 25 °C), pH 6.0 - 12.0 (optimum 7.0), and 0 - 4.0 % (w/v) NaCl (optimum 0.5 - 2.0 %). The 16 S rRNA gene-based phylogenetic analysis showed that DCL_ 24 ^T shared a 97.53 % similarity with itsºlosest type strain Rheinheimera muenzenbergensis E-49^T. Insilico DNA-DNA hybridization and average nucleotide identity values were found to be 18.60 % and 73.77 %, respectively, between the genomes of DCL_24^T and R. muenzenbergensis E-49^T. The strain DCL_24^T has 44.33 DNA G+C content (mol %). Based on the phenotypic, chemotaxonomic, and genotypic data, the strain DCL_24^T represents a novel species within the genus Rheinheimera, for which the name Rheinheimera metallidurans sp. nov is proposed. The type strain is DCL_24^T (MTCC13203^T = NBRC115780^T = JCM 35551 ^T). The isolate was found to volatilize and remove mercury efficiently, as demonstrated by X-ray film and dithizone-based colorimetric methods. Around 92 % of mercury removal was observed within 48 h. The mercury-resistant determinant mer operon consisting of merA, encoding the mercuric reductase enzyme, and transport and regulatory genes (merT, merP, merD, and merR) were found in the isolate. Relative expression analysis of merA at increasing concentrations of HgCl₂ was confirmed by quantitative real-time PCR. These data indicate the merA-mediated reduction of toxic Hg²⁺ into a non-toxic volatile Hg⁰. The phytotoxicity assay performed using Arabidopsis thaliana seeds further demonstrated the mercury toxicity reduction potential of DCL_24^T. The study shows that this novel isolate, DCL_24^T, is an interesting candidate for mercury bioremediation. However, further studies are required to assess the bioremediation efficacy of the strain under the harsh environmental conditions prevailing in polluted sites.

Candidatus Scalindua, a Biological Solution to Treat Saline Recirculating Aquaculture System Wastewater

Recirculating aquaculture systems (RAS) are promising candidates for the sustainable development of the aquaculture industry. A current limitation of RAS is the production and potential accumulation of nitrogenous wastes, ammonium (NH4+), nitrite (NO2−) and nitrate (NO3−), which could affect fish health and welfare. In a previous experiment, we have demonstrated that the marine anammox bacteria Candidatus Scalindua was a promising candidate to treat the wastewater (WW) of marine, cold-water RAS. However, the activity of the bacteria was negatively impacted after a direct exposure to RAS WW. In the current study, we have further investigated the potential of Ca. Scalindua to treat marine RAS WW in a three-phase experiment. In the first phase (control, 83 days), Ca. Scalindua was fed a synthetic feed, enriched in NH4+, NO2− and trace element (TE) mix. Removal rates of 98.9% and 99.6% for NH4+ and NO2−, respectively, were achieved. In the second phase (116 days), we gradually increased the exposure of Ca. Scalindua to nitrogen-enriched RAS WW over a period of about 80 days. In the last phase (79 days), we investigated the needs of TE supplementation for the Ca. Scalindua after they were fully acclimated to 100% RAS WW. Our results show that the gradual exposure of Ca. Scalindua resulted in a successful acclimation to 100% RAS WW, with maintained high removal rates of both NH4+ and NO2− throughout the experiment. Despite a slight decrease in relative abundance (from 21.4% to 16.7%), Ca. Scalindua remained the dominant species in the granules throughout the whole experiment. We conclude that Ca. Scalindua can be successfully used to treat marine RAS WW, without the addition of TE, once given enough time to acclimate to its new substrate. Future studies need to determine the specific needs for optimal RAS WW treatment by Ca. Scalindua at pilot scale.

Arsukibacterium indicum sp. nov., isolated from deep-sea sediment, and transfer of Rheinheimera tuosuensis and Rheinheimera perlucida to the genus Arsukibacterium as Arsukibacterium tuosuense comb. nov. and Arsukibacterium perlucidum comb. nov

A Gram-stain-negative, aerobic, flagellated and rod-shaped bacterium, designated strain SM2107T, was isolated from a deep-sea sediment sample collected from the Southwest Indian Ocean. Strain SM2107T grew at 4–40 °C and with 0–10.0 % (w/v) NaCl. It reduced nitrate to nitrite and hydrolysed casein, gelatin, chitin and DNA. The phylogenetic trees based on the 16S rRNA genes and single-copy orthologous clusters showed that strain SM2107T, together with Rheinheimera tuosuensis , Rheinheimera perlucida and Arsukibacterium ikkense , formed a separate clade, having the highest similarity to the type strain of Rheinheimera tuosuensis (98.3%). The major polar lipids were phosphatidylethanolamine and phosphatidylglycerol and the major cellular fatty acids were summed feature 8 (C18 : 1  ω7c and/or C18 : 1  ω6c), C16 : 0, C17 : 1 ω8с and summed feature 3 (C16 : 1  ω7c and/or C16 : 1  ω6c). The only respiratory quinone was Q-8. The genomic DNA G+C content of strain SM2107T was 48.8 %. The digital DNA–DNA hybridization values between strain SM2107T and type strains of Rheinheimera tuosuensis , Rheinheimera perlucida and Arsukibacterium ikkense were 41.16, 37.70 and 31.80 %, while the average amino acid identity values between them were 87.59, 86.76 and 83.64 %, respectively. Based on the polyphasic evidence presented in this study, strain SM2107T was considered to represent a novel species within the genus Arsukibacterium , for which the name Arsukibacterium indicum was proposed. The type strain is SM2107T (=MCCC M24986T=KCTC 82921T). Moreover, the transfer of Rheinheimera tuosuensis and Rheinheimera perlucida to the genus Arsukibacterium as Arsukibacterium tuosuense comb. nov. (type strain TS-T4T=CGMCC 1.12461T=JCM 19264T) and Arsukibacterium perlucidum comb. nov. (type strain BA131T=LMG 23581T=CIP 109200T) is also proposed.

Unraveling the plastic degradation potentials of the plastisphere-associated marine bacterial consortium as a key player for the low-density polyethylene degradation

The omnipresent accumulation and non-degradable nature of plastics in the environment are posing an ever-increasing ecological threat. In this study, a total of 97 bacteria were isolated from macroplastic debris collected from the coastal environments of Andaman Island. The isolates were screened for LDPE degradation potential and were identified based on phenotypic, biochemical, and molecular characterization. 16S rDNA-based identification revealed that three-three isolates of each belong to the genus Oceanimonas and Vibrio, two were closely related to the genus Paenibacillus whereas, one-one was associated with the genus Shewanella, Rheinheimera, and Bacillus, respectively. A bacterial consortium was formulated using the top four isolates based on their individual LDPE degradation potentials. A significant increase (p < 0.05) in the mean LDPE degradation (47.07 ± 6.67% weight-loss) and change in thickness was observed after 120 days of incubation. FTIR spectrum, ¹³C NMR, and TG-DSC analyses demonstrated changes in the LDPE sheets' functional groups, crystallinity, and in thermal properties after 120 days of incubation. The SEM and AFM images confirmed bacterial attachments, an increase in surface roughness and deformities on LDPE sheets. This study reports a bacterial consortium that can efficiently degrade the plastics and can be used in providing eco-friendly mitigation of plastic waste.

Rheinheimera lutimaris sp. nov., a marine bacterium isolated from coastal sediment

A Gram-stain-negative, aerobic, rod-shaped bacterium, designated strain YQF-2^T, was isolated from coastal sediment sampled in Jiangsu Province and characterized phylogenetically and phenotypically. Optimal bacterial growth occurred at 28 °C (range 4-38 °C) and pH 7 (pH 6-10). Phylogenetic analysis based on 16S rRNA gene sequences showed that strain YQF-2^T was related to members of the genus Rheinheimera and shared the highest sequence identities with Rheinheimera pacifica KMM 1406^T (98.6%), followed by Rheinheimera aestuarii H29^T (98.4%), Rheinheimera japonica KMM 9513^T (98.3%), Rheinheimera aquimaris SW-353^T (98.3%), Rheinheimera hassiensis E48^T (97.8%) and Rheinheimera muenzenbergensis E49^T (97.7%). The 16S rRNA gene sequence identities between strain YQF-2^T and other members of the genus Rheinheimera were below 97.2%. The digital DNA-DNA hybridization value between strain YQF-2^T and R. pacifica KMM 1406^T was 23.3±2.3%. The average nucleotide identity value between strain YQF-2^T and R. pacifica KMM 1406^T was 79.7%. The unique respiratory quinone was ubiquinone-8. Phosphatidylethanolamine and phosphatidylglycerol were identified as the major polar lipids. The strain had summed feature 3 (C_16:1 ω7c and/or C_16:1 ω6c), summed feature 8 (C_18:1 ω7c and/or C_18:1 ω6c), C_16:0, C_12:0 3-OH and iso-C_17:0 3-OH as major fatty acids. The G+C content of the genomic DNA was 50.0 mol%. On the basis of phenotypic, genotypic and phylogenetic evidence, strain YQF-2^T represents a novel species of the genus Rheinheimera, for which the name Rheinheimera lutimaris sp. nov. is proposed, with the type strain YQF-2^T (=KCTC 72184^T=MCCC 1K03663^T).

Interactions between immune system and the microbiome of skin, blood and gut in pathogenesis of rosacea

The increasingly wide use of next-generation sequencing technologies has revolutionised our knowledge of microbial environments associated with human skin, gastrointestinal tract and blood. The collective set of microorganisms influences metabolic processes, affects immune responses, and so directly or indirectly modulates disease. Rosacea is a skin condition of abnormal inflammation and vascular dysfunction, and its progression is affected by Demodex mites on the skin surface. When looking into the effects influencing development of rosacea, it is not only the skin microbiome change that needs to be considered. Changes in the intestinal microbiome and their circulating metabolites, as well as changes in the blood microbiome also affect the progression of rosacea. Recent research has confirmed the increased presence of bacterial genera like Acidaminococcus and Megasphera in the intestinal microbiome and Rheinheimera and Sphingobium in the blood microbiome of rosacea patients. In this review we discuss our current knowledge of the interactions between the immune system and the skin, gut and blood microbiome, with particular attention to rosacea diagnostic opportunities.

A Novel Mobile Element ICERspD18B in Rheinheimera sp. D18 Contributes to Antibiotic and Arsenic Resistance

Antibiotics and organoarsenical compounds are frequently used as feed additives in many countries. However, these compounds can cause serious antibiotic and arsenic (As) pollution in the environment, and the spread of antibiotic and As resistance genes from the environment. In this report, we characterized the 28.5 kb genomic island (GI), named as ICERspD18B, as a novel chromosomal integrative and conjugative element (ICE) in multidrug-resistant Rheinheimera sp. D18. Notably, ICERspD18B contains six antibiotic resistance genes (ARGs) and an arsenic tolerance operon, as well as genes encoding conjugative transfer proteins of a type IV secretion system, relaxase, site-specific integrase, and DNA replication or partitioning proteins. The transconjugant strain 25D18-B4 was generated using Escherichia coli 25DN as the recipient strain. ICERspD18B was inserted into 3'-end of the guaA gene in 25D18-B4. In addition, 25D18-B4 had markedly higher minimum inhibitory concentrations for arsenic compounds and antibiotics when compared to the parental E. coli strain. These findings demonstrated that the integrative and conjugative element ICERspD18B could mediate both antibiotic and arsenic resistance in Rheinheimera sp. D18 and the transconjugant 25D18-B4.

Rheinheimera mangrovi sp. nov., a bacterium isolated from mangrove sediment

A Gram-stain-negative, rod-shaped, motile and strictly aerobic bacterium, designated LHK132T, was isolated from a mangrove sediment sample collected in Haikou, Hainan Province, PR China. Strain LHK132T was able to grow at temperatures of 10–45 °C, at salinities of 0–7.0 % (w/v) and at pH 6.0–9.0. Catalase and oxidase activities, H2S production, urease and methyl red reaction were positive. Indole, nitrate reduction, hydrolysis of gelatin, starch, casein and Tweens 20, 40, 60 and 80 were negative. The major cellular fatty acids were C16 : 0 and summed feature 3 (C16 : 1  ω7c and/or C16 : 1  ω6c). The only respiratory quinone was ubiquinone-8. The major polar lipids were phosphatidylethanolamine and phosphatidylglycerol. According to 16S rRNA gene sequence analysis, strain LHK132T had 98.3, 97.5, 97.4, 97.2 and 97.1% similarities to Rheinheimera soli BD-d46T, Rheinheimera sediminis YQF-1T, Rheinheimera tangshanensis JA3-B52T, Rheinheimera mesophila IITR-13T and Rheinheimera arenilitoris J-MS1T, respectively. Phylogenetic analyses indicated that strain LHK132T formed a distinct lineage with R. soli BD-d46T within the genus Rheinheimera . The average nucleotide identity and digital DNA–DNA hybridization values between strain LHK132T and related species of the genus Rheinheimera were well below the thresholds for species delineation. The DNA G+C content was 46.7 mol%. On the basis of its phenotypic, chemotaxonomic and genotypic data, strain LHK132T is considered a representative of a novel species in the genus Rheinheimera , for which the name Rheinheimera mangrovi sp. nov. is proposed. The type strain is LHK132T (=KCTC 62580T=MCCC 1K03529T).

Rheinheimera sediminis sp. nov., a marine bacterium isolated from coastal sediment

A Gram-stain-negative, aerobic, rod-shaped bacterium, designated strain YQF-1^T, was isolated from coastal sediment in Jiangsu Province (PR China) and characterized phylogenetically and phenotypically. Bacterial optimal growth occurred at 28 °C (range 4-40 °C) and pH 7 (range pH 6-11). Phylogenetic analysis based on 16S rRNA gene sequence indicated that YQF-1^T was related to members of the genus Rheinheimera and shared the highest sequence identities with Rheinheimera mesophila DSM 29723^T (98.5 %), followed by Rheinheimera tangshanensis DSM 19460^T (98.4 %), Rheinheimera tilapiae Ruye-90^T (97.9 %), Rheinheimera soli BD-d46^T (97.9 %), Rheinheimera aquatica GR5^T (97.4 %), Rheinheimera coerulea TAPG2^T (97.3 %) and Rheinheimera texasensis A62-14B^T (97.1 %). The 16S rRNA gene sequence identities between YQF-1^T and other members of the genus Rheinheimera were below 97.0 %. The digital DNA-DNA hybridization value between YQF-1^T and Rheinheimera mesophila DSM 29723^T was 25.1±2.3 %. The average nucleotide identity (ANI) value between YQF-1^T and Rheinheimera mesophila DSM 29723^T was 81.4 %. The major respiratory quinone was Q-8. The major polar lipids were phosphatidylethanolamine, phosphatidylglycerol, phospholipid, two unidentified aminolipids and three unidentified lipids. The strain had summed feature 8 (C_18 : 1  ω7c and/or C_18 : 1  ω6c), C_16 : 0, summed feature 3 (C_16 : 1  ω7c and/or C_16 : 1  ω6c), iso-C_15 : 0, and anteiso-C_17 : 1  ω9c as the major fatty acids. The G+C content of the genomic DNA was 46.2 mol%. On the basis of phenotypic, genotypic and phylogenetic evidence, strain YQF-1^T represents a novel species of the genus Rheinheimera, for which the name Rheinheimera sediminis sp. nov. is proposed, with the type strain YQF-1^T (=KCTC 72183^T=MCCC 1K03646^T).

Potential of mercury-tolerant bacteria for bio-uptake of mercury leached from discarded fluorescent lamps

In this study, ten bacterial strains were found to be mercury resistant after their isolation from Qatari coastal sediments. Tolerance was found to be up to 100-150 ppm for five strains. Those strains had optimum growth conditions at salinity level of 10 ppm NaCl and pH 7-8. Starting from a concentration 7.9 ppm of mercury extracted from fluorescent lamps and after 6 days of incubation at 37 °C, two isolated strains HA6 (Bacillus spp.) and HA9 (Acinetobacter sp.) showed 96.7% and 98.9% of mercury bio-uptake efficiency, respectively. Other strains were capable of removing more than 60% of extracted mercury.

Rheinheimera coerulea sp. nov., isolated from a freshwater creek, and emended description of genus Rheinheimera Brettar et al. 2002

A bacterial strain designated TAPG2^T was isolated from a freshwater creek in Taiwan and characterized using the polyphasic taxonomic approach. Cells of TAPG2^T were Gram-stain negative, aerobic, motile, non-spore forming, short rods surrounded by a thick capsules and forming cream to dark-green colonies. Growth occurred at 15-37 °C (optimum, 25-30 °C), at pH 6.5-8 (optimum, pH 7) and with 0-1 % NaCl (optimum, 0.5 %). The major fatty acids (>10 %) of TAPG2^T were summed feature 3 (C16 : 1ω7c and/or C16 : 1ω6c), C16 : 0 and C18 : 1ω7c. The polar lipid profile consisted of phosphatidylethanolamine, phosphatidylglycerol, an uncharacterized aminophospholipid, an uncharacterized phospholipid, an uncharacterized aminolipid and an uncharacterized lipid. The polyamine profile was composed of the major compound putrescine and moderate amounts of spermidine. The only isoprenoid quinone was Q-8. The DNA G+C content was 53.6 mol%. Phylogenetic analyses based on 16S rRNA gene sequences indicated that TAPG2^T represented a member of the genus Rheinheimera and was most closely related to Rheinheimera aquatica GR5^T and Rheinheimera texasensis A62-14B^T with 98.6 and 98.2 % 16S rRNA gene sequence identities, respectively. However, DNA-DNA hybridization values of TAPG2^T with type strains of the species with validly published names were lower than 30 %. Differential phenotypic properties, together with the phylogenetic inference, demonstrate that TAPG2^T should be classified as representing a novel species of the genus Rheinheimera, for which the name Rheinheimera coerulea sp. nov. is presented. The type strain is TAPG2^T (=BCRC 81054^T=LMG 30056^T=KCTC 52815^T).

Rheinheimera salexigens sp. nov., isolated from a fishing hook, and emended description of the genus Rheinheimera

A Gram-negative, rod-shaped bacterium, designated KH87T, was isolated from a fishing hook that had been baited and suspended in seawater off O'ahu, Hawai'i. Based on a comparison of 1524 nt of the 16S rRNA gene sequence of strain KH87T, its nearest neighbours were the GammaproteobacteriaRheinheimera nanhaiensis E407-8T (96.2 % identity), Rheinheimera chironomi K19414T (96.0 %), Rheinheimera pacifica KMM 1406T (95.8 %), Rheinheimera muenzenbergensis E49T (95.7 %), Alishewanella solinquinati KMK6T (94.9 %) and Arsukibacterium ikkense GCM72T (94.6 %). Cells of KH87T were motile by a single polar flagellum, strictly aerobic, and catalase- and oxidase-positive. Growth occurred between 4 and 39 °C, and in a circumneutral pH range. Major fatty acids in whole cells of strain KH87T were cis-9-hexadecenoic acid, hexadecanoic acid and cis-11-octadecenoic acid. The quinone system contained mostly menaquinone MK-7, and a minor amount of ubiquinone Q-8. The polar lipid profile contained the major lipids phosphatidylglycerol, phosphatidylserine, phosphatidylethanolamine, an unidentified aminolipid, and a lipid not containing phosphate, an amino group or a sugar moiety. Putrescine was the major polyamine. Physiological, biochemical and genomic data, including obligate halophily, absence of amylolytic activity, a quinone system dominated by MK-7 and DNA G+C content (42.0 mol%) distinguished KH87T from extant Rheinheimera species; strain KH87T was also distinguished by a multi-locus sequence analysis of aligned and concatenated 16S rRNA, gyrB, rpoB and rpoD gene sequences. Based on phenotypic and genotypic differences, the species Rheinheimera salexigens sp. nov. is proposed to accommodate KH87T as the type strain (=ATCC BAA-2715T=CIP 111115T). An emended description of the genus Rheinheimera is also proposed.

Rheinheimera marina sp. nov., isolated from a deep-sea seamount

A bacterial strain designated TP462^T, isolated from a seamount near the Yap Trench in the tropical western Pacific, was characterized using a polyphasic taxonomic approach. Strain TP462^T was found to be Gram-stain-negative, aerobic, rod-shaped and motile by means of a single polar flagellum. Growth occurred at 4-37 °C (optimum, 25-30 °C) and with 0-4.0 % NaCl (optimum, 2-3 %). Phylogenetic analysis based on 16S rRNA gene sequence showed that strain TP462^T was related to the genus Rheinheimera and had the highest 16S rRNA gene sequence similarity with the type strain Rheinheimera tangshanensis JA3-B52^T (96.8 %). The predominant cellular fatty acids were C17 : 1ω8c, summed feature 3 (composed of iso-C15 : 0 2-OH and/or C16 : 1ω7c) and C16 : 0. The polar lipid profile contained phosphatidylglycerol, phosphatidylethanolamine and two unidentified lipids. The genomic DNA G+C content of strain TP462^T was 48.7 mol%. On the basis of the evidence presented in this study, strain TP462^T represents a novel species of the genus Rheinheimera, for which we propose the name Rheinheimera marina sp. nov. (type strain TP462^T=KACC 18560^T=CGMCC 1.15399^T).

Emended description of the family Chromatiaceae, phylogenetic analyses of the genera Alishewanella, Rheinheimera and Arsukibacterium, transfer of Rheinheimera longhuensis LH2-2T to the genus Alishewanella and description of Alishewanella alkalitolerans sp. nov. from Lonar Lake, India

Phylogenetic analyses were performed for members of the family Chromatiaceae, signature nucleotides deduced and the genus Alishewanella transferred to Chromatiaceae. Phylogenetic analyses were executed for the genera Alishewanella, Arsukibacterium and Rheinheimera and the genus Rheinheimera is proposed to be split, with the creation of the Pararheinheimera gen. nov. Furthermore, the species Rheinheimera longhuensis, is transferred to the genus Alishewanella as Alishewanella longhuensis comb. nov. Besides, the genera Alishewanella and Rheinheimera are also emended. Strain LNK-7.1^T was isolated from a water sample from the Lonar Lake, India. Cells were Gram-negative, motile rods, positive for catalase, oxidase, phosphatase, contained C_16:0, C_17:1ω8c, summed feature3 (C_16:1ω6c and/or C_16:1ω7c) and summed feature 8 (C_18:1ω7c) as major fatty acids, PE and PG as the major lipids and Q-8 as the sole respiratory quinone. Phylogenetic analyses using NJ, ME, ML and Maximum parsimony, based on 16S rRNA gene sequences, identified Alishewanella tabrizica RCRI4^T as the closely related species of strain LNK-7.1^T with a 16S rRNA gene sequence similarity of 98.13%. The DNA-DNA similarity between LNK-7.1^T and the closely related species (A. tabrizica) was only 12.0% and, therefore, strain LNK-7.1^T was identified as a novel species of the genus Alishewanella with the proposed name Alishewanella alkalitolerans sp. nov. In addition phenotypic characteristics confirmed the species status to strain LNK-7.1^T. The type strain of A. alkalitolerans is LNK-7.1^T (LMG 29592^T = KCTC 52279^T), isolated from a water sample collected from the Lonar lake, India.

Rheinheimera gaetbuli sp. nov., a Marine Bacterium Isolated from a Tidal Flat

A gram-staining-negative, strictly aerobic, rod-shaped, and motile bacterium with a single polar flagellum, designated H26(T), was isolated from tidal flat sediment in Jeju Island, South Korea. Growth of strain H26(T) was observed at 4-35 °C (optimum, 20-25 °C), pH 6.0-9.0 (optimum, pH 7.0-8.0), and 1-4 % NaCl (optimum, 2-3 %). Phylogenetic analyses based on 16S rRNA gene sequences showed that strain H26(T) formed a phyletic lineage within the genus Rheinheimera, family Chromatiaceae. Strain H26(T) was most closely related to Rheinheimera baltica OSBAC1(T), Rheinheimera aestuarii H29(T), Rheinheimera muenzenbergensis E49(T), and Rheinheimera aquimaris SW-353(T) with 98.5, 98.1, 97.8, and 97.5 % of 16S rRNA gene sequence similarities, respectively. The DNA-DNA relatedness levels between strain H26(T) and the type strains of R. baltica, R. aestuarii, R. muenzenbergensis, and R. aquimaris were 35.5 ± 3.2, 33.4 ± 1.5, 31.2 ± 2.2, and 28.7 ± 0.9 %, respectively. The major fatty acids of strain H26(T) were iso-C15:0 3-OH, summed feature 3 (comprising C16:1 ω7c/C16:1 ω6c), C16:0, summed feature 8 (comprising C18:1 ω7c/C18:1 ω6c), iso-C17:0 3-OH, and C12:0 3-OH and the strain contained ubiquinone (Q-8) as the sole isoprenoid quinone. Phosphatidylethanolamine, phosphatidylglycerol, and an aminolipid were identified as the major polar lipids and the G + C content of the genomic DNA was 52.0 mol%. Based on the phenotypic, chemotaxonomic, and molecular properties, strain H26(T) represents a novel species of the genus Rheinheimera, for which the name Rheinheimera gaetbuli sp. nov. is proposed. The type strain was H26(T) (=KACC 18254(T) = JCM 30403(T)).