Rheinheimera japonica sp. nov., a novel bacterium with antimicrobial activity from seashore sediments of the Sea of Japan

Relation between the relative abundance and collapse of Aphanizomenon flos-aquae and microbial antagonism in Upper Klamath Lake, Oregon

Aphanizomenon flos-aquae (AFA) is the dominant filamentous cyanobacterium that develops into blooms in Upper Klamath Lake, Oregon, each year. During AFA bloom and collapse, ecosystem conditions for endangered Lost River and shortnose suckers deteriorate, thus motivating the need to identify processes that limit AFA abundance and decline. Here, we investigate the relations between AFA and other members of the microbial community (photosynthetic and nonphotosynthetic bacteria and archaea), how those relations impact abundance and collapse of AFA, and the types of microbial conditions that suppress AFA. We found significant spatial variation in AFA relative abundance during the 2016 bloom period using 16S rRNA sequencing. The Pelican Marina site had the lowest AFA relative abundance, and this was coincident with increased relative abundance of Candidatus Sericytochromatia, Flavobacterium, and Rheinheimera, some of which are known AFA antagonists. The AFA collapse coincided with phosphorus limitation relative to nitrogen and the increased relative abundance of Cyanobium and Candidatus Sericytochromatia, which outcompete AFA when dissolved inorganic nitrogen is available. The data collected in this study indicate the importance of dissolved inorganic nitrogen combined with microbial community structure in suppressing AFA abundance.

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.

Marine Bacterial Secondary Metabolites: A Treasure House for Structurally Unique and Effective Antimicrobial Compounds

The prevalence of antimicrobial resistance reduces the effectiveness of antimicrobial drugs in preventing and treating infectious diseases caused by pathogenic organisms, such as bacteria, fungi, and viruses. Because of the burgeoning growth of microbes with antimicrobial-resistant traits, there is a dire need to identify and develop novel and effective antimicrobial agents to treat infections from antimicrobial-resistant strains. The marine environment is rich in ecological biodiversity and can be regarded as an untapped resource for prospecting novel bioactive compounds. Therefore, exploring the marine environment for antimicrobial agents plays a significant role in drug development and biomedical research. Several earlier scientific investigations have proven that bacterial diversity in the marine environment represents an emerging source of structurally unique and novel antimicrobial agents. There are several reports on marine bacterial secondary metabolites, and many are pharmacologically significant and have enormous promise for developing effective antimicrobial drugs to combat microbial infections in drug-resistant pathogens. In this review, we attempt to summarize published articles from the last twenty-five years (1996–2020) on antimicrobial secondary metabolites from marine bacteria evolved in marine environments, such as marine sediment, water, fauna, and flora.

Bacterial Communities in Concrete Reflect Its Composite Nature and Change with Weathering

Concrete is an extreme but common environment and is home to microbial communities adapted to alkaline, saline, and oligotrophic conditions. Microbes inside the concrete that makes up buildings or roads have received little attention despite their ubiquity and capacity to interact with the concrete. Because concrete is a composite of materials which have their own microbial communities, we hypothesized that the microbial communities of concrete reflect those of the concrete components and that these communities change as the concrete ages. Here, we used a 16S amplicon study to show how microbial communities change over 2 years of outdoor weathering in two sets of concrete cylinders, one prone to the concrete-degrading alkali-silica reaction (ASR) and the other having the risk of the ASR mitigated. After identifying and removing taxa that were likely laboratory or reagent contaminants, we found that precursor materials, particularly the large aggregate (gravel), were the probable source of ∼50 to 60% of the bacteria observed in the first cylinders from each series. Overall, community diversity decreased over 2 years, with temporarily increased diversity in warmer summer months. We found that most of the concrete microbiome was composed of Proteobacteria, Firmicutes, and Actinobacteria, although community composition changed seasonally and over multiyear time scales and was likely influenced by environmental deposition. Although the community composition between the two series was not significantly different overall, several taxa, including Arcobacter, Modestobacter, Salinicoccus, Rheinheimera, Lawsonella, and Bryobacter, appear to be associated with ASR.

IMPORTANCE Concrete is the most-used building material in the world and a biologically extreme environment, with a microbiome composed of bacteria that likely come from concrete precursor materials, aerosols, and environmental deposition. These microbes, though seeded from a variety of materials, are all subject to desiccation, heating, starvation, high salinity, and very high pH. Microbes that survive and even thrive under these conditions can potentially either degrade concrete or contribute to its repair. Thus, understanding which microbes survive in concrete, under what conditions, and for how long has potential implications for biorepair of concrete. Further, methodological pipelines for analyzing concrete microbial communities can be applied to concrete from a variety of structures or with different types of damage to identify bioindicator species that can be used for structural health monitoring and service life prediction.

Rheinheimera pleomorphica sp. nov., a Novel Alkali-Tolerant Bacteria Isolated from Chilika Lake, India

A novel Gram-negative gamma-proteobacterium, non-sporulating motile, rod or coccus-shaped bacterium designated as strain PKS7^T was isolated from a sediment sample collected from Chilika Lake, Odisha, India and characterized taxonomically using a polyphasic approach. The major quinone was Q8 and major cellular fatty acids were C_16:0, C_17:0, C_15:1w8c_, C_17:1w8c, C_12:03-OH. The chemotaxonomic features confirmed the isolate to be a member of genus Rheinheimera. 16SrRNA gene sequence of strain PKS7^T was closest in similarity to R. aquimaris SW-353^T (99.36% identity), R. muenzenbergensis E49^T (98.63%), R. nanhaiensis E407-8^T (98.35%), R. japonica KMM 9513^T (98.35%) and R. baltica DSM-14885^T (98.08%). The 16S rRNA gene sequence-based phylogenetic analysis and sequence similarity between the isolated strain and type strains also revealed its affiliation to genus Rheinheimera. DNA-DNA relatedness with closest type strain R. aquimaris SW-353^T was 25.0% (±3.40) and in silico DDH showed values in the range of 17.7-37.1% with the type strains of the genus Rheinheimera for which whole genome sequence are available. Strain PKS7^T was also distinguished by a multi-locus sequence analysis (MLST) by alingning gyrB gene sequences of the closest type strains of Rheinheimera. The draft genome of strain PKS7^T contained 32 contigs of total size 3,963,569 bp comprising of 3763 predicted coding sequences with a G + C content of 50.7 mol%. Comparision of phenotypic and genotypic data with its closest neighbours and closely related species confirm the strain PKS7^T to be recognised as a novel species within the genus Rheinheimera, for which the name Rheinheimera pleomorphica sp. nov. is proposed. The type strain is PKS7^T (= KCTC 42365 = JCM 30460).

Harmful Effect of Rheinheimera sp. EpRS3 (Gammaproteobacteria) Against the Protist Euplotes aediculatus (Ciliophora, Spirotrichea): Insights Into the Ecological Role of Antimicrobial Compounds From Environmental Bacterial Strains

Rheinheimera sp. strain EpRS3, isolated from the rhizosphere of Echinacea purpurea, is already known for its ability to produce antibacterial compounds. By use of culture experiments, we verified and demonstrated its harmful effect against the ciliated protist Euplotes aediculatus (strain EASCc1), which by FISH experiments resulted to harbor in its cytoplasm the obligate bacterial endosymbiont Polynucleobacter necessarius (Betaproteobacteria) and the secondary endosymbiont "Candidatus Nebulobacter yamunensis" (Gammaproteobacteria). In culture experiments, the number of ciliates treated both with liquid broth bacteria-free (Supernatant treatment) and bacteria plus medium (Tq treatment), decreases with respect to control cells, with complete disappearance of ciliates within 6 h after Tq treatment. Results suggest that Rheinheimera sp. EpRS3 produces and releases in liquid culture one or more bioactive molecules affecting E. aediculatus survival. TEM analysis of control (not treated) ciliates allowed to morphologically characterize both kind of E. aediculatus endosymbionts. In treated ciliates, collected soon after the arising of cell suffering leading to death, TEM observations revealed some ultrastructural damages, indicating that P. necessarius endosymbionts went into degradation and vacuolization after both Supernatant and Tq treatments. Additionally, TEM investigation showed that when the ciliate culture was inoculated with Tq treatment, both a notable decrease of P. necessarius number and an increase of damaged and degraded mitochondria occur. FISH experiments performed on treated ciliates confirmed TEM results and, by means of the specific probe herein designed, disclosed the presence of Rheinheimera sp. EpRS3 both inside phagosomes and free in cytoplasm in ciliates after Tq treatment. This finding suggests a putative ability of Rheinheimera sp. EpRS3 to reintroduce itself in the environment avoiding ciliate digestion.

Moss habitats distinctly affect their associated bacterial community structures as revealed by the high-throughput sequencing method

To better understand the factors that influence the distribution of bacteria associated with mosses, the communities inhabiting in five moss species from two different habitats in Beijing Songshan National Nature Reserve were investigated using the high-throughput sequencing method. The sequencing was performed based on the bacterial 16S rRNA and 16S rDNA libraries. Results showed that there are abundant bacteria inhabiting in all the mosses sampled. The taxonomic analysis of these bacteria showed that they mainly consisted of those in the phyla Proteobacteria and Actinobacteria, and seldom were from phylum Armatimonadetes, Bacteroidetes and Firmicutes. The hierarchical cluster tree, based on the OTU level, divided the bacteria associated with all samples into two branches according to the habitat types of the host (terrestrial and aquatic). The PCoA diagram further divided the bacterial compositions into four groups according to both types of habitats and the data sources (DNA and RNA). There were larger differences in the bacterial community composition in the mosses collected from aquatic habitat than those of terrestrial one, whether at the DNA or RNA level. Thus, this survey supposed that the habitat where the host was growing was a relevant factor influencing bacterial community composition. In addition, the bacterial community detected at the RNA level was more sensitive to the habitat of the growing host, which could also be proved by the significantly differences in the predicted function by PICRUSt and the metabolically active dominant genera between different groups. This study expands the knowledge about the interactions between mosses and microbes.

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).

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

A Gram-negative, rod-shaped bacterium, designated KH87^T, 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 KH87^T, its nearest neighbours were the GammaproteobacteriaRheinheimera nanhaiensis E407-8^T (96.2 % identity), Rheinheimera chironomi K19414^T (96.0 %), Rheinheimera pacifica KMM 1406^T (95.8 %), Rheinheimera muenzenbergensis E49^T (95.7 %), Alishewanella solinquinati KMK6^T (94.9 %) and Arsukibacterium ikkense GCM72^T (94.6 %). Cells of KH87^T 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 KH87^T 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 KH87^T from extant Rheinheimera species; strain KH87^T 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 KH87^T as the type strain (=ATCC BAA-2715^T=CIP 111115^T). An emended description of the genus Rheinheimera is also proposed.

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.

Antibacterial low-molecular-weight compounds produced by the marine bacterium Rheinheimera japonica KMM 9513T

Strain KMM 9513^T was isolated from a sediment sample collected from the Sea of Japan seashore and selected due to its ability to inhibit indicator bacterial growth. The strain KMM 9513^T has been recently described as a novel species Rheinheimera japonica. This study was undertaken to determine which substances produced by strain KMM 9513^T could be responsible for its antimicrobial activity. Eight compounds were obtained from an ethyl acetate extract of R. japonica KMM 9513^T. The structures of five diketopiperazines (4-8) and diisobutyl-, dibutyl- and bis(2-ethylhexyl) phthalates (1-3) were established on the basis of detailed interpretation of NMR data, by Marfey method and optical rotation data. The structures of diketopiperazines were determined as cyclo-(L-valyl-L-proline), cyclo-(L-valyl-D-proline), cyclo-(L-phenylalanyl-L-proline), cyclo-(L-leucyl-L-proline), and cyclo-(L-phenylalanyl-D-proline). Compounds 1-3, 5 and 8 revealed antimicrobial activities against Bacillus subtilis and/or Enterococcus faecium and Staphylococcus aureus. In this paper, we describe the isolation and structural elucidation of the isolated compounds 1-8. This is the first report of the characterisation of low molecular weight antibacterial metabolites produced by a member of the genus Rheinheimera.

List of new names and new combinations previously effectively, but not validly, published

The purpose of this announcement is to effect the valid publication of the following effectively published new names and new combinations under the procedure described in the Bacteriological Code (1990 Revision). Authors and other individuals wishing to have new names and/or combinations included in future lists should send three copies of the pertinent reprint or photocopies thereof, or an electronic copy of the published paper to the IJSEM Editorial Office for confirmation that all of the other requirements for valid publication have been met. It is also a requirement of IJSEM and the ICSP that authors of new species, new subspecies and new combinations provide evidence that types are deposited in two recognized culture collections in two different countries. Note that the date of valid publication of these new names and combinations is the date of publication of this list, not the date of the original publication of the names and combinations. The authors of the new names and combinations are as given below. Inclusion of a name on these lists validates the publication of the name and thereby makes it available in the nomenclature of prokaryotes. The inclusion of a name on this list is not to be construed as taxonomic acceptance of the taxon to which the name is applied. Indeed, some of these names may, in time, be shown to be synonyms, or the organisms may be transferred to another genus, thus necessitating the creation of a new combination.