Genome insights into the plant growth-promoting bacterium Saccharibacillus brassicae ATSA2T

Endophytes can facilitate the improvement of plant growth and health in agriculturally important crops, yet their genomes and secondary metabolites remain largely unexplored. We previously isolated Saccharibacillus brassicae strain ATSA2^T from surface-sterilized seeds of kimchi cabbage and represented a novel species of the genus Saccharibacillus. In this study, we evaluated the plant growth-promoting (PGP) effect of strain ATSA2^T in kimchi cabbage, bok choy, and pepper plants grown in soils. We found a significant effect on the shoot and root biomass, and chlorophyll contents following strain ATSA2^T treatment. Strain ATSA2^T displayed PGP traits such as indole acetic acid (IAA, 62.9 μg/mL) and siderophore production, and phosphate solubilization activity. Furthermore, genome analysis of this strain suggested the presence of gene clusters involved in iron acquisition (fhuABD, afuABC, fbpABC, and fepCDG) and phosphate solubilization (pstABCHS, phoABHLU, and phnCDEP) and other phytohormone biosynthesis genes, including indole-3-acetic acid (trpABCDEFG), in the genome. Interestingly, the secondary metabolites cerecidin, carotenoid, siderophore (staphylobactin), and bacillaene underlying plant growth promotion were found in the whole genome via antiSMASH analysis. Overall, physiological testing and genome analysis data provide comprehensive insights into plant growth-promoting mechanisms, suggesting the relevance of strain ATSA2^T in agricultural biotechnology.

Isolation of Saccharibacillus WB17 strain from wheat bran phyllosphere and genomic insight into the cellulolytic and hemicellulolytic complex of the Saccharibacillus genus

The microorganisms living on the phyllosphere (the aerial part of the plants) are in contact with the lignocellulosic plant cell wall and might have a lignocellulolytic potential. We isolated a Saccharibacillus strain (Saccharibacillus WB17) from wheat bran phyllosphere and its cellulolytic and hemicellulolytic potential was investigated during growth onto wheat bran. Five other type strains from that genus selected from databases were also cultivated onto wheat bran and glucose. Studying the chemical composition of wheat bran residues by FTIR after growth of the six strains showed an important attack of the stretching C-O vibrations assigned to polysaccharides for all the strains, whereas the C = O bond/esterified carboxyl groups were not impacted. The genomic content of the strains showed that they harbored several CAZymes (comprised between 196 and 276) and possessed four of the fifth modules reflecting the presence of a high diversity of enzymes families. Xylanase and amylase activities were the most active enzymes with values reaching more than 4746 ± 1400 mIU/mg protein for the xylanase activity in case of Saccharibacillus deserti KCTC 33693 T and 452 ± 110 mIU/mg protein for the amylase activity of Saccharibacillus WB17. The total enzymatic activities obtained was not correlated to the total abundance of CAZyme along that genus. The Saccharibacillus strains harbor also some promising proteins in the GH30 and GH109 modules with potential arabinofuranosidase and oxidoreductase activities. Overall, the genus Saccharibacillus and more specifically the Saccharibacillus WB17 strain represent biological tools of interest for further biotechnological applications.

Polyphasic characterization of and genomic insights into a haloalkali-tolerant Saccharibacillus alkalitolerans sp. nov., that produces three cellulase isozymes and several antimicrobial compounds

A cellulase producing novel bacterial strain VR-M41^T was isolated from an open-air vegetable and fruit market. Cells are found to be rod-shaped, endospore forming, positive for Gram's stain and negative for catalase, oxidase and urease. Strain VR-M41^T was halotolerant (upto 8.0% NaCl, w/v), motile and facultative anaerobe. It grew at wide range of pH (6.0-10.0) and temperatures (20-40 °C). Strain VR-M41^T produced three isozymes of Carboxymethylcellulase. The 16S rRNA gene sequence of strain VR-M41^T was 97.3% similar to both Saccharibacillus kuerlensis DSM 22868^T and Saccharibacillus sacchari DSM 19268^T, and less than 96.4% with the rest of the valid species of the genus Saccharibacillus. Whole-genome ANI, dDDH and genome phylogenetic tree analysis revealed that strain VR-M41^T significantly differed from Saccharibacillus kuerlensis DSM 22868^T and Saccharibacillus sacchari DSM 19268^T (ANI 79.6-79.7% and dDDH 23.1%). The strain comprised of MK-7 and anteiso-C 15:0 (42.2%) as predominant isoprenoid quinone and fatty acid respectively. Major polar lipids were found to be diphosphatidylglycerol, phosphatidylglycerol and phosphatidylethanolamine. The draft genome of strain VR-M41^T consisted of 5,386,426 base pairs with 5103 annotated genes, out of which 2147 corresponded to hypothetical proteins and 2956 with functional assignments. Pan-genome analysis revealed the presence of 2998 core genes, 828 accessory genes, and 1131 unique genes of Saccharibacillus. Strain VR-M41^T produced antimicrobials against Staphylococcus aureus, Streptococcus pneumoniae, Micrococcus luteus and Shigella flexneri. Significant phenotypic and genotypic differentiating characteristics from closely related species, indicated that strain VR-M41^T is a novel species of the genus Saccharibacillus, for which the name Saccharibacillus alkalitolerans sp. nov., is proposed. The type strain is VR-M41^T (= KCTC 43183^T=NBRC 114337^T).

Draft Genome Sequence of Saccharibacillus sp. Strain WB 17, Isolated from Wheat Phyllosphere

The whole genome of Saccharibacillus sp. strain WB 17, a bacterial strain isolated from wheat phyllosphere, has been sequenced. This microorganism is equipped with several carbohydrate-active enzymes, which would explain its ability to fractionate lignocellulose.

The whole genome of Saccharibacillus sp. strain WB 17, a bacterial strain isolated from wheat phyllosphere, has been sequenced. This microorganism is equipped with several carbohydrate-active enzymes, which would explain its ability to fractionate lignocellulose.

Whole-genome sequence data and analysis of Saccharibacillus sp. ATSA2 isolated from Kimchi cabbage seeds

Saccharibacillus sp. ATSA2 was isolated from Kimchi cabbage seeds grown in Gyeongbuk province in the Republic of Korea. Whole-genome sequencing of Saccharibacillus sp. ATSA2 was performed using the PacBio RSII and Illumina HiSeq platforms, and it features a 5,619,468 bp circular chromosome with 58.4% G + C content. The genome includes 4543 protein-coding genes, 104 RNA genes (70 transfer RNA genes, 30 ribosomal RNA genes, and 4 non-coding RNA), and 73 pseudogenes. Multiple gene clusters associated with stress responses, nitrogen and phosphorus metabolism, and plant hormone biosynthesis were annotated in the genome. The genome information will provide fundamental knowledge of this organism as well as insight for understanding microbial activity in the agricultural application. The whole-genome sequence of Saccharibacillus sp. ATSA2 is available at GenBank/EMBL/DDBJ under accession number CP041217.

Saccharibacillus endophyticus sp. nov., an endophyte of cotton

A Gram-positive-staining, facultatively aerobic, endospore-forming bacterial strain, isolated from the stem tissue of cotton (Gossypium hirsutum) was subjected to a detailed taxonomic study using a polyphasic approach. Based on 16S rRNA gene sequence similarity comparisons, strain JM-1350T grouped into the genus Saccharibacillus, and was most closely related to the type strain of Saccharibacillus sacchari (96.5 % 16S rRNA gene sequence similarity), followed by the type strains of Saccharibacillus kuerlensis (96.3 %) and Saccharibacillus deserti (95.1 %). The diagnostic diamino acid of the peptidoglycan was meso-diaminopimelic acid. The quinone system contained exclusively menaquinone MK-7. The polar lipid (L1) profile consisted of the major lipids diphosphatidylglycerol and phosphatidylglycerol and moderate amounts of three glycolipids and an aminophospholipid and a polar lipid (L1). The major fatty acids were iso- and anteiso-branched fatty acids. The genomic G+C content was 55.2 mol%. In addition, the results of physiological and biochemical tests allowed phenotypic differentiation of strain JM-1350T from all closely related species. Thus, strain JM-1350T represents a novel species of the genus Saccharibacillus, for which the name Saccharibacillus endophyticus sp. nov. is proposed. The type strain is JM-1350T (=LMG 29710T=CCM 8702T).

Saccharibacillus qingshengii sp. nov., isolated from a lead-cadmium tailing

A Gram-stain-positive, strictly aerobic strain, H6T, was isolated from a soil sample of lead-cadmium tailing in Qixia district, Nanjing (China). Cells of the strain are rod-shaped and colonies on LB agar are red. Strain H6T has subpolar and polar flagella and the optimal condition for growth is 30 °C, with 1 % (w/v) NaCl and at pH 7.0. Based on the 16S rRNA gene sequences, phylogenetic analysis showed that strain H6T was closely related to the genus Saccharibacillus, and the closest relatives were Saccharibacillus deserti WLJ055T (99.0 % 16S rRNA gene sequence similarity), Saccharibacillus kuerlensis HR1T (97.0 %) and Saccharibacillus sacchari GR21T (96.4 %). The DNA-DNA relatedness value between strain H6T and S. deserti WLJ055T was 55.0 %. The major polar lipids of strain H6T were diphosphatidylglycerol, phosphatidylglycerol, phosphoglycolipid and three unknown glycolipids. The DNA G+C content was 58.4 mol% and MK-7 was the major isoprenoid quinone. The major fatty acids were anteiso-C15 : 0 and C16 : 0. meso-Diaminopimelic acid was detected in the peptidoglycan. Based on the phylogenetic, biochemical and chemotaxonomic data, strain H6T represents a novel species of the genus Saccharibacillus, for which the name Saccharibacillus qingshengii sp. nov., is proposed. The type strain is H6T (=CCTCC AB 2016001T=JCM 31172T).

Saccharibacillus deserti sp. nov., isolated from desert soil

A Gram-stain-positive, facultatively anaerobic bacterial strain, designated WLJ055T, with polar and subpolar flagella was isolated from the top layer of desert soil from Erdos, Inner Mongolia, northern China. Phylogenetic analysis, based on 16S rRNA gene sequences, revealed that strain WLJ055T was a member of the genus Saccharibacillus, and shared 97.17-97.24 % 16S rRNA gene sequence similarities with Saccharibacillus sacchari GR21T and Saccharibacillus kuerlensis HR1T. The major polar lipids of strain WLJ055T were diphosphatidylglycerol, phosphatidylglycerol, an unknown aminophospholipid, two unknown glycolipids and an unknown phosphoglycolipid. MK-7 was the predominant menaquinone, while anteiso-C15 : 0, C16 : 0, iso-C16 : 0, and anteiso-C17 : 0 were the major cellular fatty acids. Its genomic DNA G+C content was 55.5 mol%. DNA-DNA hybridization revealed that strain WLJ055T showed 45 ± 5 % and 40 ± 5 % genomic DNA relatedness with its two closest relatives, S. sacchari GR21T and S. kuerlensis HR1T, respectively. The results of physiological and biochemical tests allowed the discrimination of strain WLJ055T from its phylogenetic relatives. Saccharibacillus deserti sp. nov. is therefore proposed to be a novel species of the genus Saccharibacillus, with strain WLJ055T ( = CGMCC 1.15276T = KCTC 33693T) as the type strain.

Ammoniibacillus agariperforans gen. nov., sp. nov., a thermophilic, agar-degrading bacterium isolated from compost

A thermophilic, agar-degrading bacterium, strain FAB2(T), was isolated from sewage sludge compost. According to phylogenetic analysis based on 16S rRNA gene sequences, strain FAB2(T) belonged to the family Paenibacillaceae within the phylum Firmicutes. However, FAB2(T) was different enough at the genus level from closely related species. The percentages of 16S rRNA gene sequence similarity with related organisms were 90.4 % for Thermobacillus xylanilyticus, 91.8 % for Paenibacillus barengoltzii, 89.4 % for Cohnella lupini, 90.1 % for Fontibacillus aquaticus, and 89.0 % for Saccharibacillus sacchari. Morphological and physiological analyses revealed that the strain was motile, rod-shaped, Gram-stain-positive, aerobic and able to form oval endospores in swollen sporangia. Ammonium was required as a nitrogen source while nitrate, nitrite, urea and glutamate were not utilized. Catalase and oxidase activities were weakly positive and positive, respectively. The bacterium grew in the temperature range of 50-65 °C and in media with pH 7.5 to 9.0. Optimal growth occurred at 60 °C and pH 8.0-8.6. Growth was inhibited at pH≤7.0 and NaCl concentrations ≥2.5 % (w/v). In chemotaxonomic characterization, MK-7 was identified as the dominant menaquinone. Major fatty acids were iso-C16 : 0 and C16 : 0. Dominant polar lipids were diphosphatidylglycerol, phosphatidylglycerol and phosphatidylethanolamine. Phosphatidylcholine was present in a moderate amount. The diamino acid in the cell wall was meso-diaminopimelic acid. The G+C content of the genomic DNA was 49.5 mol% in a nucleic acid study. On the basis of genetic and phenotypic characteristics, strain FAB2(T) ( = NBRC 109510(T) = KCTC 33130(T)) showed characteristics suitable for classification as the type strain of a novel species of a new genus in the family Paenibacillaceae, for which the name Ammoniibacillus agariperforans gen. nov., sp. nov. is proposed.

The bacteria and bacteriophages from a Mesquite Flats site of the Death Valley desert

Arid zones cover over 30 % of the Earth's continental surface. In order to better understand the role of microbes in this type of harsh environment, we isolated and characterized the bacteriophages from samples of the surface sand of the Mesquite Flats region via electron microscopy and DNA sequencing of a select number of cloned phage DNAs. An electron microscopic analysis of the recovered virus-like particles revealed at least 11 apparently different morphotypes sharing structural characteristics of the Caudoviridae family of tailed phages. We found that 36 % of the sequences contained no significant identity (e-value >10(-3)) with sequences in the databases. Pilot sequencing of cloned 16S rRNA genes identified Bacteroidetes and Proteobacteria as the major bacterial groups present in this severe environment. The majority of the 16S rDNA sequences from the total (uncultured) bacterial population displayed ≤96 % identity to 16S rRNA genes in the database, suggesting an unexplored bacterial population likely adapted to a desert environment. In addition, we also isolated and identified 38 cultivable bacterial strains, the majority of which belonged to the genus Bacillus. Mitomycin-C treatment of the cultivable bacteria demonstrated that the vast majority (84 %) contained at least one SOS-inducible prophage.