Whole genome sequencing of a Domibacillus strain from the Cuatro Ciénegas basin that tends to act as an altruist

Domibacillus sp. 8LH is a whitish bacterium isolated from the pools of the Cuatro Cienegas Basin (CCB) in the state of Coahuila and belongs to the Bacillaceae family. It grows in circular colonies of about 6 mm in diameter and is capable of forming biofilms. This strain was identified because, in previous experiments in our laboratory, it presented altruistic interactions when co-cultured with bacteria of the genus Bacillus that participate in the nitrogen cycle. This altruistic behavior confers to this Domibacillus strain a potential use for the construction of bacterial consortia with diverse biotechnological applications.

Bacillales: From Taxonomy to Biotechnological and Industrial Perspectives

For a long time, the genus Bacillus has been known and considered among the most applicable genera in several fields. Recent taxonomical developments resulted in the identification of more species in Bacillus-related genera, particularly in the order Bacillales (earlier heterotypic synonym: Caryophanales), with potential application for biotechnological and industrial purposes such as biofuels, bioactive agents, biopolymers, and enzymes. Therefore, a thorough understanding of the taxonomy, growth requirements and physiology, genomics, and metabolic pathways in the highly diverse bacterial order, Bacillales, will facilitate a more robust designing and sustainable production of strain lines relevant to a circular economy. This paper is focused principally on less-known genera and their potential in the order Bacillales for promising applications in the industry and addresses the taxonomical complexities of this order. Moreover, it emphasizes the biotechnological usage of some engineered strains of the order Bacillales. The elucidation of novel taxa, their metabolic pathways, and growth conditions would make it possible to drive industrial processes toward an upgraded functionality based on the microbial nature.

Endophytic Bacteria Colonizing the Petiole of the Desert Plant Zygophyllum dumosum Boiss: Possible Role in Mitigating Stress

Zygophyllum dumosum is a dominant shrub in the Negev Desert whose survival is accomplished by multiple mechanisms including abscission of leaflets to reduce whole plant transpiration while leaving the fleshy, wax-covered petioles alive but dormant during the dry season. Petioles that can survive for two full growing seasons maintain cell component integrity and resume metabolic activity at the beginning of the winter. This remarkable survival prompted us to investigate endophytic bacteria colonizing the internal tissues of the petiole and assess their role in stress tolerance. Twenty-one distinct endophytes were isolated by culturing from surface-sterile petioles and identified by sequencing of the 16S rDNA. Sequence alignments and the phylogenetic tree clustered the isolated endophytes into two phyla, Firmicutes and Actinobacteria. Most isolated endophytes displayed a relatively slow growth on nutrient agar, which was accelerated by adding petiole extracts. Metabolic analysis of selected endophytes showed several common metabolites whose level is affected by petiole extract in a species-dependent manner including phosphoric acid, pyroglutamic acid, and glutamic acid. Other metabolites appear to be endophyte-specific metabolites, such as proline and trehalose, which were implicated in stress tolerance. These results demonstrate the existence of multiple endophytic bacteria colonizing Z. dumosum petioles with the potential role in maintaining cell integrity and functionality via synthesis of multiple beneficial metabolites that mitigate stress and contribute to stress tolerance.

Diversity of cultivable bacteria from deep-sea sediments of the Colombian Caribbean and their potential in bioremediation

The diversity of deep-sea cultivable bacteria was studied in seven sediment samples of the Colombian Caribbean. Three hundred and fifty two marine bacteria were isolated according to its distinct morphological character on the solid media, then DNA sequences of the 16S rRNA were amplified to identify the isolated strains. The identified bacterial were arranged in three phylogenetic groups, Firmicutes, Proteobacteria, and Actinobacteria, with 34 different OTUs defined at ≥ 97% of similarity and 70 OTUs at ≥ 98.65%, being the 51% Firmicutes, 34% Proteobacteria and 15% Actinobacteria. Bacillus and Fictibacillus were the dominant genera in Firmicutes, Halomonas and Pseudomonas in Proteobacteria and Streptomyces and Micromonospora in Actinobacteria. In addition, the strains were tested for biosurfactants and lipolytic enzymes production, with 120 biosurfactant producing strains (mainly Firmicutes) and, 56 lipolytic enzymes producing strains (Proteobacteria). This report contributes to the understanding of the diversity of the marine deep-sea cultivable bacteria from the Colombian Caribbean, and their potential application as bioremediation agents.

The Diversity and Geographic Distribution of Cultivable Bacillus-Like Bacteria Across Black Soils of Northeast China

Bacillus-like species are gram-positive bacteria that are ubiquitous in soils. Many of Bacillus-like bacteria are demonstrated as beneficial microbes widely used in industry and agriculture. However, the knowledge related to their diversity and distribution patterns in soils is still rudimentary. In this study, we developed a combined research method of using culture-dependent and high-throughput sequencing to investigate the composition and diversity of cultivable Bacillus-like bacterial communities across 26 soil samples obtained from the black soil zone in northeast China. Nearly all bacterial 16S rDNA sequences were classified into the order Bacillales. Fifteen genera were detected, with Bacillus, Paenibacillus, and Brevibacillus being the three most abundant genera. Although more than 2,000 OTUs were obtained across all samples, 33 OTUs were confirmed as the abundant species with a relative abundance over 5% in at least one sample. Pairwise analysis showed that the diversity of Bacillus-like bacterial communities were significantly and positively correlated with soil total carbon contents and soil sampling latitudes, which suggests that a latitudinal gradient diversity of Bacillus-like bacterial communities exists in the black soil zone. The principal coordinates analysis revealed that the Bacillus-like bacterial communities were remarkably affected by soil sampling latitudes and soil total carbon content. In general, this study demonstrated that a distinct biogeographic distribution pattern of cultivable Bacillus-like bacterial communities existed in the black soil zone, which emphasizes that the strategy of local isolation and application of beneficial Bacillus-like strains is rather important in black soil agriculture development.

Examination into the taxonomic position of Bacillus thermotolerans Yang et al., 2013, proposal for its reclassification into a new genus and species Quasibacillus thermotolerans gen. nov., comb. nov. and reclassification of B. encimensis Dastager et al., 2015 as a later heterotypic synonym of B. badius

Two novel Gram-staining positive, rod-shaped, moderately halotolerant, endospore forming bacterial strains 5.5LF 38TD and 5.5LF 48TD were isolated and taxonomically characterized from a landfill in Chandigarh, India. The analysis of 16S rRNA gene sequences of the strains confirmed their closest identity to Bacillus thermotolerans SgZ-8T with 99.9% sequence similarity. A comparative phylogenetic analysis of strains 5.5LF 38TD, 5.5LF 48TD and B. thermotolerans SgZ-8^T confirmed their separation into a novel genus with B. badius and genus Domibacillus as the closest phylogenetic relatives. The major fatty acids of the strains are iso-C_15:0 and iso-C_16:0 and MK-7 is the only quinone. The major polar lipids are diphosphatidylglycerol, phosphatidylglycerol and phosphatidylethanolamine. The digital DNA-DNA hybridization (DDH) and ortho average nucleotide identity (ANI) values calculated through whole genome sequences indicated that the three strains showed low relatedness with their phylogenetic neighbours. Based on evidences from phylogenomic analyses and polyphasic taxonomic characterization we propose reclassification of the species B. thermotolerans into a novel genus named Quasibacillus thermotolerans gen. nov., comb. nov with the type strain SgZ-8^T (=CCTCC AB2012108^T=KACC 16706^T). Further our analyses also revealed that B. encimensis SGD-V-25^T is a later heterotypic synonym of Bacillus badius DSM 23^T.

Domibacillus antri sp. nov., isolated from the soil of a cave

A Gram-reaction-positive, strictly aerobic, capsule-forming, motile and rod-shaped bacterium, designated strain XD80^T, was isolated from the soil of a native cave in Lichuan, Hubei province, China. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain XD80^T was most closely related to Domibacillus iocasae CCTCC AB 2015183^T (98.66 % sequence similarity), followed by Domibacillus robiginosus DSM 25058^T(97.83 %), Domibacillus tundrae KCTC 33549^T (97.70 %), Domibacillus enclensis CCTCC AB 2011121^T (97.21 %) and Domibacillus indicus DSM 28032^T (96.96 %). Levels of DNA-DNA relatedness between strain XD80^T and D. iocasae CCTCC AB 2015183^T, D. robiginosusDSM 25058^T, D. tundrae KCTC 33549^T and D. enclensis CCTCC AB 2011121^T were 37.4 %, 53.8 %, 53.6 % and 52.7 %, respectively. The major polar lipids were diphosphatidylglycerol, phosphatidylglycerol, aminophospholipid and two unknown phospholipids. The predominant fatty acids (>5 %) were iso-C15 : 0 (37.3 %), anteiso-C15 : 0 (10.8 %), C16 : 0 (10.4 %), iso-C17 : 0 (10.3 %), C16 : 1ω11c (9.6 %) and anteiso-C17 : 0 (7.4 %). MK-6 (86.4 %) was the major respiratory quinone. The DNA G+C content was 46.4 mol%. The cell-wall peptidoglycan contained meso-diaminopimelic acid (type A1γ). Ribose and glucose were the major whole-cell sugars. In addition, strain XD80^T showed differential physiological characteristics from most members of the genus Domibacillus, encompassing hydrolysis of starch, acid production from inositol and raffinose, and production of valine arylamidase. The results of this polyphasic study indicated that strain XD80^T represents a novel species of the genus Domibacillus, for which the name Domibacillus antri sp. nov. is proposed. The type strain is XD80^T (=CCTCC AB 2015053^T=KCTC 33636^T).

Ecology of Bacillaceae

Members of the family Bacillaceae are among the most robust bacteria on Earth, which is mainly due to their ability to form resistant endospores. This trait is believed to be the key factor determining the ecology of these bacteria. However, they also perform fundamental roles in soil ecology (i.e., the cycling of organic matter) and in plant health and growth stimulation (e.g., via suppression of plant pathogens and phosphate solubilization). In this review, we describe the high functional and genetic diversity that is found within the Bacillaceae (a family of low-G+C% Gram-positive spore-forming bacteria), their roles in ecology and in applied sciences related to agriculture. We then pose questions with respect to their ecological behavior, zooming in on the intricate social behavior that is becoming increasingly well characterized for some members of Bacillaceae. Such social behavior, which includes cell-to-cell signaling via quorum sensing or other mechanisms (e.g., the production of extracellular hydrolytic enzymes, toxins, antibiotics and/or surfactants) is a key determinant of their lifestyle and is also believed to drive diversification processes. It is only with a deeper understanding of cell-to-cell interactions that we will be able to understand the ecological and diversification processes of natural populations within the family Bacillaceae. Ultimately, the resulting improvements in understanding will benefit practical efforts to apply representatives of these bacteria in promoting plant growth as well as biological control of plant pathogens.

Domibacillus tundrae sp. nov., isolated from active layer soil of tussock tundra in Alaska, and emended description of the genus Domibacillus

A novel Gram-stain-positive, spore-forming, aerobic, motile and rod-shaped bacterium designated strain PAMC 80007T was isolated from an active layer soil sample of Council, Alaska. Optimal growth of strain PAMC 80007T was observed at 30 °C, pH 7.0 and in the presence of 2 % (w/v) NaCl. Phylogenetic analysis based on 16S rRNA gene sequence indicated that strain PAMC 80007T belonged to the genus Domibacillus. This strain was closely related to Domibacillus enclensis (98.3 %), Domibacillus robiginosus (98.3 %) and Domibacillus indicus (97.2 %). Genomic DNA G+C content was 43.5 mol% and genomic relatedness analyses based on the average nucleotide identity and the genome-to-genome distance showed that strain PAMC 80007T is clearly distinguished from the closely related species of the genus Domibacillus. The major fatty acids (>5 %) were iso-C15 : 0 (24.7 %), C16 : 1ω11c (16.8 %), anteiso-C15 : 0 (16.5 %), C16 : 0 (15.6 %) and anteiso-C17 : 0 (8.7 %). The major respiratory isoprenoid quinones were menaquinone-6 (MK-6) and menaquinone-7 (MK-7), and the polar lipid profile contained diphosphatidylglycerol, phosphatidylglycerol, phosphoglycolipid, phospholipid and two unidentified lipids. meso-Diaminopimelic acid (type A1γ) was present in the cell-wall peptidoglycan, and the major whole-cell sugar was ribose with a minor quantity of glucose. Results from a polyphasic study suggested that strain PAMC 80007T represents a novel species of the genus Domibacillus for which the name Domibacillus tundrae sp. nov. is proposed. The type strain is PAMC 80007T ( = JCM 30371T = KCTC 33549T = DSM 29572T). An emended description of the genus Domibacillus is also provided.

Domibacillus enclensis sp. nov., isolated from marine sediment, and emended description of the genus Domibacillus

A novel red-pigmented bacterial strain, designated NIO-1016(T), was isolated from a sediment sample from Chorao Island, India and was investigated by a polyphasic taxonomic approach. The strain was Gram-reaction-positive, strictly aerobic, motile and catalase-positive and produced spherical to slightly ellipsoidal endospores with subterminal position on swollen sporangia. The genomic DNA G+C content was 46.9 mol%. The major fatty acids were anteiso-C15 : 0, anteiso-C17 : 0, iso-C15 : 0 and C16 : 0. The predominant quinones were MK-6 (89.3 %) and MK-7 (8.7 %). The polar lipids consisted of diphosphatidylglycerol, phosphatidylglycerol, and an unidentified phospholipid. meso-Diaminopimelic acid (type A1γ) was present in the cell-wall peptidoglycan and the major whole-cell sugars were glucose and ribose. The closest phylogenetic neighbours were identified as Domibacillus robiginosus DSM 25058(T) (98.0 % similarity) and Domibacillus indicus DSM 28032(T) (97.2 % similarity), other species of the genus Bacillus displayed below 96 % similarity. Phylogenetic, physiological, biochemical and morphological differences between strain NIO-1016(T) and its closest neighbours indicate that this strain represents a novel species in the genus Domibacillus in the family Bacillaceae for which the name Domibacillus enclensis sp. nov. is proposed with the type species NIO-1016(T) ( = DSM 25145(T) = NCIM 5462(T) = CCTCC AB 2011121(T)).

Description of Domibacillus indicus sp. nov., isolated from ocean sediments and emended description of the genus Domibacillus

A novel Gram-stain-positive, spore-forming, aerobic, non-motile, rod-shaped bacterium designated strain SD111(T) that forms red-pigmented colonies was isolated from a marine sediment sample (collected from 5 m depth) from Lakshadweep, India. Strain SD111(T) grew well on seawater agar at pH 6-10 (optimum pH 7.5±0.2). It showed maximum (97.6 %) 16S rRNA gene sequence similarity and formed a monophyletic clade with Domibacillus robiginosus WS 4628(T) ( = DSM 25058(T)). The genomic DNA G+C content was 37.4 mol% and the strain showed 37.7 % DNA-DNA relatedness to D. robiginosus DSM 25058(T). The major fatty acids were anteiso-C15 : 0, C16 : 0, iso-C15 : 0 and iso-C16 : 0 and MK-6 was the predominant quinone. The polar lipid profile of strain SD111(T) consisted of unidentified phospholipids (PL1 and PL2), phosphatidylglycerol (PG) and diphosphatidylglycerol (DPG). The cell wall contained meso-diaminopimelic acid and the peptidoglycan was of A1γ type. Glucose and ribose were detected as major cell-wall sugars. Results from polyphasic studies indicated that SD111(T) represents a novel species of the genus Domibacillus for which the name Domibacillus indicus sp. nov. is proposed. The type strain is SD111(T) ( = MCC 2255(T) = DSM 28032(T)).

Virgibacillus halotolerans sp. nov., isolated from a dairy product

A Gram-stain-positive, strictly aerobic, rod-shaped and weakly motile bacterium, designated WS 4627T, was isolated from a dairy product sample collected in southern Germany. Spherical to slightly ellipsoidal endospores were formed centrally or subterminally in sometimes slightly swollen sporangia. The isolate was able to grow at 8–35 °C, at pH 6.5–8.5 and with 0.5–16.5 % (w/v) NaCl. The diamino acid of the cell wall was meso-diaminopimelic acid (peptidoglycan type A1γ) and the genomic DNA G+C content was 39.1 mol%. The major menaquinone was MK-7, the cellular fatty acid profile contained major amounts of anteiso-C15 : 0 and anteiso-C17 : 0 and the major polar lipids were diphosphatidylglycerol and phosphatidylglycerol. Strain WS 4627T was most closely related to ‘ Virgibacillus natachei’ FarD (96.5 % 16S rRNA gene sequence similarity) and ‘ Virgibacillus zhanjiangensis’ JSM 079157 (96.0 %). Based on the data presented, strain WS 4627T represents a novel species of the genus Virgibacillus , for which the name Virgibacillus halotolerans sp. nov. is proposed. The type strain is WS 4627T ( = DSM 25060T = LMG 26644T).