Structural and functional changes in soil bacterial communities by drifting spray application of a commercial red seaweed extract as revealed by metagenomics

Kappaphycus alvarezii seaweed extract (KSWE) is known to enhance crop productivity and impart stress tolerance. Close to one quarter of foliar spray applied to maize falls on the soil, either as drift or from leaf as drip. It was hypothesized that the drift spray would profoundly influence soil microbes under stress. An experiment was conducted with five treatments, with or without KSWE application at critical stages of maize grown under soil moisture stress and compared with an irrigated control. An Illumina platform was employed for the analysis of the V3-V4 region of 16S rRNA gene from the soil metagenome. A total of 345,552 operational taxonomic units were generated which were classified into 55 phyla, 152 classes, 240 orders, 305 families and 593 genera. Shannon's index and Shannon's equitability indicated increased soil bacterial diversity after multiple KSWE applications under conditions of abiotic duress. The abundance of the genera Alicyclobacillus, Anaerolinea, Bacillus, Balneimonas, Nitrospira, Rubrobacter and Steroidobacter decreased (49-79%) under drought imposed at the V5,10 and 15 stages of maize over the irrigated control, while it significantly improved when followed by KSWE application under drought. Flavobacterium, Nitrosomonas, Nitrosovibrio, Rubrobacter genera and several other bacterial taxa which are important for plant growth promotion and nutrient cycling were found to be enriched by KSWE application under drought conditions. Treatments having enriched microbial abundance due to KSWE application under stress recorded higher soil enzymatic activities and plant cob yield, suggesting the contribution of altered soil ecology mediated by KSWE as one of the reasons for improvement of yield.

From ecophysiology to cultivation methodology: filling the knowledge gap between uncultured and cultured microbes

Earth is dominated by a myriad of microbial communities, but the majority fails to grow under in situ laboratory conditions. The basic cause of unculturability is that bacteria dominantly occur as biofilms in natural environments. Earlier improvements in the culture techniques are mostly done by optimizing media components. However, with technological advancement particularly in the field of genome sequencing and cell imagining techniques, new tools have become available to understand the ecophysiology of microbial communities. Hence, it becomes easier to mimic environmental conditions in the culture plate. Other methods include co-culturing, emendation of growth factors, and cultivation after physical cell sorting. Most recently, techniques have been proposed for bacterial cultivation by employing genomic data to understand either microbial interactions (network-directed targeted bacterial isolation) or ecosystem engineering (reverse genomics). Hopefully, these techniques may be applied to almost all environmental samples, and help fill the gaps between the cultured and uncultured microbial communities.

Lentibacillus cibarius sp. nov., isolated from kimchi, a Korean fermented food

Two bacterial strains designated NKC220-2^T and NKC851-2 were isolated from commercial kimchi from different areas in Korea. The strains were Gram-positive, aerobic, oxidaseand catalase-positive, rod-shaped, spore-forming, non-motile, and halophilic bacteria. Both strains grew without NaCl, unlike type species in the genus Lentibacillus. The optimal pH for growth was 8.0, higher than that of the type species in the genus Lentibacillus, although growth was observed at pH 5.5-9.0. 16S rRNA gene sequence-based phylogenetic analysis indicated that the two strains (99.3-99.9% similarity) are grouped within the genus Lentibacillus and most closely related to Lentibacillus juripiscarius IS40-3^T (97.4-97.6% similarity) isolated from fish sauce in Thailand. OrthoANI value between two novel strains and Lentibacillus lipolyticus SSKP1-9^T (79.5-79.6% similarity) was far lower than the species demarcation threshold. Comparative genomic analysis displayed differences between the two strains as well as among other strains belonging to Lentibacillus. Furthermore, each isolate had strain-specific groups of orthologous genes based on pangenome analysis. Genomic G + C contents of strains NKC-220-2^T and NKC851-2 were 41.9 and 42.2 mol%, respectively. The strains contained meso-diaminopimelic acid in their cell walls, and the major menaquinone was menaquinone-7. Phosphatidylglycerol, diphosphatidylglycerol, and an unidentified glycolipid, aminophospholipid, and phospholipid were the major polar lipid components of both strains. The major cellular fatty acids of the strains were anteiso-C_15:0 and anteiso-C_17:0. Based on phenotypic, genomic, phylogenetic, and chemotaxonomic features, strains NKC220-2^T and NKC851-2 represent novel species of the genus Lentibacillus, for which the name Lentibacillus cibarius sp. nov. is proposed. The type strain is NKC220-2^T (= KACC 21232^T = JCM 33390^T).

Lentibacillus lipolyticus sp. nov., a moderately halophilic bacterium isolated from shrimp paste (Ka-pi)

A Gram-stain-positive, aerobic, spore-forming, moderately halophilic bacterium, SSKP1-9^T, was isolated from traditional salted shrimp paste (Ka-pi) produced in Samut Sakhon Province, Thailand. This strain grew optimally at 37-40 °C, pH 7.0 and in the presence of 8-16 % (w/v) NaCl. The 16S rRNA gene sequence similarity values between strain SSKP1-9^T and Lentibacillus juripiscarius TISTR 1535^T and Lentibacillus halophilus TISTR 1549^T were 98.7 and 97.2 %, respectively. Based on 16S rRNA gene sequence similarity, strain SSKP1-9^T represents a distinct novel species, as shown by phenotypic traits, DNA-DNA hybridization and average nucleotide identity values. In addition, the whole-cell protein profile confirmed the novelty of the taxon. The genomic DNA G+C content was 44.6 mol%. The major isoprenoid quinone was MK-7. The cell-wall peptidoglycan contained meso-diaminopimelic acid. Polar lipid analysis revealed the presence of phosphatidylglycerol, diphosphatidylglycerol, four unidentified lipids, an unidentified phospholipid and an unidentified glycolipid. The major cellular fatty acids were anteiso-C_15 : 0, anteiso-C_17 : 0 and iso-C_16 : 0. The results of phenotypic and chemotaxonomic characteristics and whole-genome analysis support that strain SSKP1-9^T represents a novel species of Lentibacillus, for which the name Lentibacilluslipolyticus sp. nov. is proposed. The type strain is SSKP1-9^T (=JCM 32625^T=TISTR 2597^T).

Evolution in the Bacillaceae

The family Bacillaceae constitutes a phenotypically diverse and globally ubiquitous assemblage of bacteria. Investigation into how evolution has shaped, and continues to shape, this family has relied on several widely ranging approaches from classical taxonomy, ecological field studies, and evolution in soil microcosms to genomic-scale phylogenetics, laboratory, and directed evolution experiments. One unifying characteristic of the Bacillaceae , the endospore, poses unique challenges to answering questions regarding both the calculation of evolutionary rates and claims of extreme longevity in ancient environmental samples.

Salisediminibacterium halotolerans gen. nov., sp. nov., a halophilic bacterium from soda lake sediment

An orange-pigmented, Gram-reaction-positive, non-spore-forming, halophilic, alkali-tolerant rod, designated strain halo-2T, was isolated from sediment of Xiarinaoer soda lake, in China’s Inner Mongolia Autonomous Region. Strain halo-2T grew in a complex medium with 3–30 % (w/v) NaCl and at pH 5–10. The cell-wall peptidoglycan contained meso-diaminopimelic acid and the major respiratory isoprenoid quinone was MK-7. The predominant cellular fatty acids were anteiso-C15 : 0 (43.6 %), anteiso-C17 : 0 (14.8 %) and iso-C15 : 0 (6.8 %) and the polar lipids consisted of diphosphatidylglycerol, phosphatidylethanolamine and phosphatidylglycerol. The genomic DNA G+C content of the novel strain was 48.2 mol%. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain halo-2T was most closely related to Bacillus agaradhaerens DSM 8721T (93.9 % sequence similarity). However, strain halo-2T could be clearly differentiated from its closest phylogenetic relatives on the basis of several phenotypic, genotypic and chemotaxonomic characteristics. Strain halo-2T therefore represents a novel species in a new genus for which the name Salisediminibacterium halotolerans gen. nov., sp. nov. is proposed. The type strain of the type species is halo-2T ( = CGMCC 1.7654T = NBRC 104935T).

Identification of moderately halophilic bacteria from Thai fermented fish ( pla-ra ) and proposal of Virgibacillus siamensis sp. nov

Forty-one isolates of moderately halophilic bacteria were isolated from fermented fish (pla-ra) in Thailand. On the basis of their phenotypic and chemotaxonomic characteristics, DNA-DNA relatedness and 16S rRNA gene sequences analyses, they were divided into six groups. The isolates in Group I to V were Gram-positive rod-shaped bacteria. They contained meso-diaminopimelic acid in the cell-wall peptidoglycan and menaquinone with seven isoprene units (MK-7). An isolate in Group VI was a Gram-negative rod-shaped bacterium. The DNA G+C contents of tested strains ranged from 36.5-63 mol%. Ten strains (Group I) were identified as Virgibacillus dokdonensis, 13 isolates (Group II) as V. halodenitrificans, 14 isolates (Group III) as V. marismortui, 1 isolate (Group IV) as Virgibacillus sp., 2 isolates (Group V) as Bacillus vietnamnensis, and 1 isolate (Group VI) as Chromohalobacter salexigens. Isolate MS3-4 in Group IV was closely related to V. carmonensis KCTC 3819(T) (95.9%). This strain contained anteiso-C(15:0) (55.8%) and anteiso-C(17:0) (17.7%) as major cellular fatty acids and had phosphatidylglycerol, diphosphatidylglycerol and an unidentified glycolipid as polar lipids. The DNA G+C content of MS3-4 was 38.0 mol%. The strain from Group IV is proposed as Virgibacillus siamensis sp. nov. and MS3-4(T) is the type strain (JCM 15395(T) =PCU 312(T) =TISTR 1957(T)).

Lentibacillus jeotgali sp. nov., a halophilic bacterium isolated from traditional Korean fermented seafood

A novel, Gram-positive, non-motile, endospore-forming and moderately halophilic bacterium, strain GrbiT, was isolated from a traditional Korean fermented seafood. The organism grew optimally in the presence of 10–15 % NaCl, at 37 °C and pH 8.0. The peptidoglycan of the cell wall consisted of meso-diaminopimelic acid, and the predominant menaquinone was MK-7. The major fatty acids of strain GrbiT were iso-C16 : 0 (36.4 %), anteiso-C15 : 0 (30.3 %) and iso-C14 : 0 (18.2 %). The polar lipids were phosphatidylglycerol, diphosphatidylglycerol and an unidentified glycolipid. The genomic DNA G+C content was 42.5 mol%. Strain GrbiT was most closely related to the type strain Lentibacillus kapialis JCM 12580T, with which it shared 97.5 % 16S rRNA gene sequence similarity. The DNA–DNA hybridization value between strains GrbiT and L. kapialis JCM 12580T was 8 %. Based on phenotypic, genotypic and phylogenetic data, strain GrbiT should be classified as a novel species within the genus Lentibacillus, for which the name Lentibacillus jeotgali sp. nov. is proposed. The type strain is GrbiT (=KCTC 13300T=JCM 15795T).

Lentibacillus persicus sp. nov., a moderately halophilic species isolated from a saline lake

A Gram-staining-positive, moderately halophilic bacterium, designated strain Amb31(T), was isolated from water of the hypersaline lake Aran-Bidgol in Iran and characterized taxonomically using a polyphasic approach. Cells were rods, motile and able to produce ellipsoidal endospores at a central position in swollen sporangia. Strain Amb31(T) was facultatively anaerobic and catalase- and oxidase-positive. The strain grew in a complex medium supplemented with 3-25 % (w/v) NaCl (optimum 7.5-10 %). Optimal growth was at 30-35 degrees C and pH 7.5. Phylogenetic analysis based on 16S rRNA gene sequence comparisons showed that strain Amb31(T) belonged to the genus Lentibacillus; it exhibited 16S rRNA gene sequence similarity values of 96.8 and 96.4 % to Lentibacillus salicampi SF-20(T) and Lentibacillus salinarum AHS-1(T), respectively, and values of 95.9-94.7 % to the type strains of other recognized species of Lentibacillus. The cell-wall peptidoglycan of strain Amb31(T) was based on meso-diaminopimelic acid and MK-7 was the respiratory isoprenoid quinone. The major fatty acids were anteiso-C(15 : 0) (44.7 %), iso-C(16 : 0) (21.4 %) and anteiso-C(17 : 0) (15.9 %) and the polar lipid pattern consisted of phosphatidylglycerol, diphosphatidylglycerol, five phospholipids and a glycolipid. The DNA G+C content was 44.1 mol%. All these features confirmed the placement of strain Amb31(T) within the genus Lentibacillus and the strain could be clearly differentiated from strains of the other species of Lentibacillus on the basis of several phenotypic, genotypic and chemotaxonomic features. DNA-DNA relatedness with the type strain of the most closely related strain, L. salicampi DSM 16425(T), was 28 %. Therefore, strain Amb31(T) represents a novel species of the genus Lentibacillus, for which the name Lentibacillus persicus sp. nov. is proposed. The type strain is Amb31(T) (=CCM 7683(T) =CECT 7524(T) =DSM 22530(T) =LMG 25304(T)).