Enhancing spinach (Spinacia oleracea L.) resilience in pesticide-contaminated soil: Role of pesticide-tolerant Ciceribacter azotifigens and Serratia marcescens in root architecture, leaf gas exchange attributes and antioxidant response restoration.

This study unveils the detoxification potential of insecticide-tolerant plant beneficial bacteria (PBB), i.e., Ciceribacter azotifigens SF1 and Serratia marcescens SRB1, in spinach treated with fipronil (FIP), profenofos (PF) and chlorantraniliprole (CLP) insecticides. Increasing insecticide doses (25-400 µg kg-1 soil) significantly curtailed germination attributes and growth of spinach cultivated at both bench-scale and in greenhouse experiments. Profenofos at 400 µg kg-1 exhibited maximum inhibitory effects and reduced germination by 55%; root and shoot length by 78% and 81%, respectively; dry matter accumulation in roots and shoots by 79% and 62%, respectively; leaf number by 87% and leaf area by 56%. Insecticide application caused morphological distortion in root tips/surfaces, increased levels of oxidative stress, and cell death in spinach. Application of insecticide-tolerant SF1 and SRB1 strains relieved insecticide pressure resulting in overall improvement in growth and physiology of spinach grown under insecticide stress. Ciceribacter azotifigens improved germination rate (10%); root biomass (53%); shoot biomass (25%); leaf area (10%); Chl-a (45%), Chl-b (36%) and carotenoid (48%) contents of spinach at 25 µg CLP kg-1 soil. PBB inoculation reinvigorated the stressed spinach and modulated the synthesis of phytochemicals, proline, malondialdehyde (MDA), superoxide anions (O2•-), and hydrogen peroxide (H2O2). Scanning electron microscopy (SEM) revealed recovery in root tip morphology and stomatal openings on abaxial leaf surfaces of PBB-inoculated spinach grown with insecticides. Ciceribacter azotifigens inoculation significantly increased intrinsic water use efficiency, transpiration rate, vapor pressure deficit, intracellular CO2 concentration, photosynthetic rate, and stomatal conductance in spinach exposed to 25 µg FIP kg-1. Also, C. azotifigens and S. marcescens modulated the antioxidant defense systems of insecticide-treated spinach. Bacterial strains were strongly colonized to root surfaces of insecticide-stressed spinach seedlings as revealed under SEM. The identification of insecticide-tolerant PBBs such as C. azotifigens and S. marcescens hold the potential for alleviating abiotic stress to spinach, thereby fostering enhanced and safe production within polluted agroecosystems.

Lysinibacillus xylanilyticus Strain GIC41 as a Potential Plant Biostimulant.

To identify Lysinibacillus strains with the potential to function as plant biostimulants, we screened 10 previously isolated Lysinibacillus strains from the rhizosphere and soil for their plant growth-promoting (PGP) effects. In vitro tests showed that all strains produced indole-3-acetic acid. In primary screening, the PGP effects of these strains were assessed on spinach seedlings grown on Jiffy-7 pellets; strains GIC31, GIC41, and GIC51 markedly promoted shoot growth. In secondary screening, the PGP efficacies of these three strains were examined using spinach seedlings grown in pots under controlled conditions. Only GIC41 exerted consistent and significant PGP effects; therefore, it was selected for subsequent experiments. The results of 6-week glasshouse experiments revealed that GIC41 markedly increased shoot dry weight by ca. 12-49% over that of the control. The impact of fertilization levels on the PGP efficacy of GIC41 was investigated using pot experiments. The application of a specific level of fertilizer was required for the induction of sufficient PGP effects by this strain. The phylogenetic ana-lysis based on the 16S rDNA sequence identified GIC41 as L. xylanilyticus. Collectively, these results show the potential of strain GIC41 to function as a plant biostimulant.

Evaluation of probiotic properties of Lysinibacillus macroides under in vitro conditions and culture of Cyprinus carpio on growth parameters.

Cyprinus carpio is an important freshwater fish in aquaculture. It was used for the isolation of potential probiotic strain for aquaculture applications. The most dominant strain was isolated on MRS agar from the gastrointestinal (GI) of C. carpio and identified as Lysinibacillus macroides using molecular marker 16S rRNA gene. Various probiotic properties such as acid and bile tolerance and antibiotic susceptibility were analysed under in vitro conditions. Further, formulate pelletized feed using probiotic (L. macroides) in different concentrations (2, 4, 6 and 8%). Rearing of C. carpio was carried out 45 days and fed with formulated feed. The highest length (5.14 ± 0.07 cm) and weight (3.56 ± 0.07 g) of C. carpio fingerlings was recorded in the 8% LM probiotic pelletized feed, while in fingerlings fed with control showed lower in the length (3.02 ± 0.13 cm) and the weight (0.92 ± 0.04 g) on the 45th day of the experiment. Both percentage of weight gain (PWG) and specific growth rate (SGR) were significantly increased (P < 0.05) of C. carpio fingerlings fed with probiotic feed compared to control feed. Hence, the use of probiotic bacteria could be an encouraging alternative feed for future endeavours in the field of aquaculture. In conclusion, L. macroides can serve as probiotic for sustainable, competitive and promising beneficial bacteria to aquaculture industry.

Salicibibacter cibarius sp. nov. and Salicibibacter cibi sp. nov., two novel species of the family Bacillaceae isolated from kimchi.

To date, all species in the genus Salicibibacter have been isolated in Korean commercial kimchi. We aimed to describe the taxonomic characteristics of two strains, NKC5-3T and NKC21-4T, isolated from commercial kimchi collected from various regions in the Republic of Korea. Cells of these strains were rod-shaped, Gram-positive, aerobic, oxidase- and catalase-positive, non-motile, halophilic, and alkalitolerant. Both strains, unlike other species of the genus Salicibibacter, could not grow without NaCl. Strains NKC5-3T and NKC21-4T could tolerate up to 25.0% (w/v) NaCl (optimum 10%) and grow at pH 7.0-10.0 (optimum 8.5) and 8.0-9.0 (optimum 8.5), respectively; they showed 97.1% 16S rRNA gene sequence similarity to each other and were most closely related to S. kimchii NKC1-1T (97.0% and 96.8% similarity, respectively). The genome of strain NKC5-3T was nearly 4.6 Mb in size, with 4,456 protein-coding sequences (CDSs), whereas NKC21-4T genome was nearly 3.9 Mb in size, with 3,717 CDSs. OrthoANI values between the novel strains and S. kimchii NKC1-1T were far lower than the species demarcation threshold. NKC5-3T and NKC21-4T clustered together to form branches that were distinct from the other Salicibibacter species. The major fatty acids in these strains were anteiso-C15:0 and anteiso-C17:0, and the predominant menaquinone was menaquinone-7. The polar lipids of NKC5-3T included diphosphatidylglycerol (DPG), phosphatidylglycerol (PG), and five unidentified phospholipids (PL), and those of NKC21-4T included DPG, PG, seven unidentified PLs, and an unidentified lipid. Both isolates had DPG, which is the first case in the genus Salicibibacter. The genomic G + C content of strains NKC5-3T and NKC21-4T was 44.7 and 44.9 mol%, respectively. Based on phenotypic, genomic, phylogenetic, and chemotaxonomic analyses, strains NKC5-3T (= KACC 22040T = DSM 111417T) and NKC21-4T (= KACC 22041T = DSM 111418T) represent two novel species of the genus Salicibibacter, for which the names Salicibibacter cibarius sp. nov. and Salicibibacter cibi sp. nov. are proposed.

Characterization of the major antifungal extrolite from rice endophyte Lysinibacillus sphaericus against Rhizoctonia solani.

Sheath blight of rice caused by Rhizoctonia solani is regarded as one of the most widely distributed diseases of rice, and is one of the major production constraints for rice in India and most rice-growing countries of Asia. Biological control of plant diseases using antagonistic bacteria is now considered as a promising alternative to the use of hazardous chemical fungicides or bactericides. Several bacterial endophytes have been reported to support growth and improve the health of the plants and therefore, may be important as biocontrol agents. In the present study, putative antifungal metabolites were extracted from rice foliage endophyte Lysinibacillus sphaericus KJ872548 by solvent extraction methods and purified using HPTLC techniques. Separated bands were subjected to assess the in vitro antagonistic activity toward rice sheath blight pathogen Rhizoctonia solani using a dual culture method. Partially purified active fraction B2 obtained from HPTLC analysis showed the highest percentage of inhibition (76.9%). GC MS and FTIR analyses of B2 revealed the compound as1, 2-Benzenedicarboxylic acid butyl 2-Ethylhexyl ester, a strong antifungal volatile organic compound. Light microscopic analysis of the fungal mycelium from the dual culture plate of both culture filtrate and 1, 2-Benzenedicarboxylic acid butyl 2-Ethylhexyl ester disclosed strong mycolytic activity as evident by mycelial distractions and shrinkage. This is the first report on antifungal production by endophytic Lysinibacillus sphaericus against R. solani, the rice sheath blight pathogen. The findings of this study biologically prospect the endophyte L. sphaericus as an inexpensive broad spectrum bioagent for eco-friendly, economic and sustainable agriculture.

Characterization of Lysinibacillus fusiformis strain S4C11: In vitro, in planta, and in silico analyses reveal a plant-beneficial microbe.

Despite sharing many of the traits that have allowed the genus Bacillus to gain recognition for its agricultural relevance, the genus Lysinibacillus is not as well-known and studied. The present study employs in vitro, in vivo, in planta, and in silico approaches to characterize Lysinibacillus fusiformis strain S4C11, isolated from the roots of an apple tree in northern Italy. The in vitro and in vivo assays demonstrated that strain S4C11 possesses an antifungal activity against different fungal pathogens, and is capable of interfering with the germination of Botrytis cinerea conidia, as well as of inhibiting its growth through the production of volatile organic molecules. In planta assays showed that the strain possesses the ability to promote plant growth, that is not host-specific, both in controlled conditions and in a commercial nursery. Biocontrol assays carried out against phytopathogenic viruses gave contrasting results, suggesting that the strain does not activate the host's defense pathways. The in silico analyses were carried out by sequencing the genome of the strain through an innovative approach that combines Illumina and High-Definition Mapping methods, allowing the reconstruction of a main chromosome and two plasmids from strain S4C11. The analysis of the genes encoded by the genome contributed to the characterization of the strain, detecting genes related to the biocontrol effect detected in the experimental trials.

A systematic review of the genera Geobacillus and Parageobacillus: their evolution, current taxonomic status and major applications.

The genus Geobacillus, belonging to the phylum Firmicutes, is one of the most important genera and comprises thermophilic bacteria. The genus Geobacillus was erected with the taxonomic reclassification of various Bacillus species. Taxonomic studies of Geobacillus remain in progress. However, there is no comprehensive review of the characteristic features, taxonomic status and study of various applications of this interesting genus. The main aim of this review is to give a comprehensive account of the genus Geobacillus. At present the genus acomprises 25 taxa, 14 validly published (with correct name), nine validly published (with synonyms) and two not validly published species. We describe only validly published species of the genera Geobacillus and Parageobacillus. Vegetative cells of Geobacillus species are Gram-strain-positive or -variable, rod-shaped, motile, endospore-forming, aerobic or facultatively anaerobic, obligately thermophilic and chemo-organotrophic. Growth occurs in the pH range 6.08.5 and a temperature of 37-75 °C. The major cellular fatty acids are iso-C15:o, iso-C16:0 and iso-C17:o. The main menaquinone type is MK-7. The G-+C content of the DNA ranges between 48.2 and 58 mol%. The genus Geobacillus is widely distributed in nature, being mostly found in many extreme locations such as hot springs, hydrothermal vents, marine trenches, hay composts, etc. Geobacillus species have been widely exploited in various industrial and biotechnological applications, and thus are promising candidates for further studies in the future.

Impacts of plant growth promoters and plant growth regulators on rainfed agriculture.

Demand for agricultural crop continues to escalate in response to increasing population and damage of prime cropland for cultivation. Research interest is diverted to utilize soils with marginal plant production. Moisture stress has negative impact on crop growth and productivity. The plant growth promoting rhizobacteria (PGPR) and plant growth regulators (PGR) are vital for plant developmental process under moisture stress. The current study was carried out to investigate the effect of PGPR and PGRs (Salicylic acid and Putrescine) on the physiological activities of chickpea grown in sandy soil. The bacterial isolates were characterized based on biochemical characters including Gram-staining, P-solubilisation, antibacterial and antifungal activities and catalases and oxidases activities and were also screened for the production of indole-3-acetic acid (IAA), hydrogen cyanide (HCN) and ammonia (NH3). The bacterial strains were identified as Bacillus subtilis, Bacillus thuringiensis and Bacillus megaterium based on the results of 16S-rRNA gene sequencing. Chickpea seeds of two varieties (Punjab Noor-2009 and 93127) differing in sensitivity to drought were soaked for 3 h before sowing in fresh grown cultures of isolates. Both the PGRs were applied (150 mg/L), as foliar spray on 20 days old seedlings of chickpea. Moisture stress significantly reduced the physiological parameters but the inoculation of PGPR and PGR treatment effectively ameliorated the adverse effects of moisture stress. The result showed that chickpea plants treated with PGPR and PGR significantly enhanced the chlorophyll, protein and sugar contents. Shoot and root fresh (81%) and dry weights (77%) were also enhanced significantly in the treated plants. Leaf proline content, lipid peroxidation and antioxidant enzymes (CAT, APOX, POD and SOD) were increased in reaction to drought stress but decreased due to PGPR. The plant height (61%), grain weight (41%), number of nodules (78%) and pod (88%), plant yield (76%), pod weight (53%) and total biomass (54%) were higher in PGPR and PGR treated chickpea plants grown in sandy soil. It is concluded from the present study that the integrative use of PGPR and PGRs is a promising method and eco-friendly strategy for increasing drought tolerance in crop plants.

Salicibibacter halophilus sp. nov., a moderately halophilic bacterium isolated from kimchi.

A Gram-stain-positive, rod-shaped, alkalitolerant, and halophilic bacterium-designated as strain NKC3-5T-was isolated from kimchi that was collected from the Geumsan area in the Republic of Korea. Cells of isolated strain NKC3-5T were 0.5-0.7 µm wide and 1.4-2.8 µm long. The strain NKC3-5T could grow at up to 20.0% (w/v) NaCl (optimum 10%), pH 6.5-10.0 (optimum pH 9.0), and 25-40°C (optimum 35°C). The cells were able to reduce nitrate under aerobic conditions, which is the first report in the genus Salicibibacter. The genome size and genomic G + C content of strain NKC3-5T were 3,754,174 bp and 45.9 mol%, respectively; it contained 3,630 coding sequences, 16S rRNA genes (six 16S, five 5S, and five 23S), and 59 tRNA genes. Phylogenetic analysis based on 16S rRNA showed that strain NKC3-5T clustered with bacterium Salicibibacter kimchii NKC1-1T, with a similarity of 96.2-97.6%, but formed a distinct branch with other published species of the family Bacillaceae. In addition, OrthoANI value between strain NKC3-5T and Salicibibacter kimchii NKC1-1T was far lower than the species demarcation threshold. Using functional genome annotation, the result found that carbohydrate, amino acid, and vitamin metabolism related genes were highly distributed in the genome of strain NKC3-5T. Comparative genomic analysis revealed that strain NKC3-5T had 716 pan-genome orthologous groups (POGs), dominated with carbohydrate metabolism. Phylogenomic analysis based on the concatenated core POGs revealed that strain NKC3-5T was closely related to Salicibibacter kimchii. The predominant polar lipids were phosphatidylglycerol and two unidentified lipids. Anteiso-C15:0, iso-C17:0, anteiso-C17:0, and iso-C15:0 were the major cellular fatty acids, and menaquinone-7 was the major isoprenoid quinone present in strain NKC3-5T. Cell wall peptidoglycan analysis of strain NKC3-5T showed that meso-diaminopimelic acid was the diagnostic diamino acid. The phephenotypic, genomic, phylogenetic, and chemotaxonomic properties reveal that the strain represents a novel species of the genus Salicibibacter, for which the name Salicibibacter halophilus sp. nov. is proposed, with the type strain NKC3-5T (= KACC 21230T = JCM 33437T).

An alkaliphilic bacterium BKH4 of Bakreshwar hot spring pertinent to bioconcrete technology.

AIMS: Hot springs have always drawn attention due to their unique chemical richness and the presence of different microbial communities. The use of hot spring bacteria in concrete technology is our primary focus; isolation of an alkaliphilic bacterium from the Bakreshwar hot springs having longer survival and better efficacy towards cementitious environment was the basis of our study's design. METHODS AND RESULTS: A novel facultative anaerobic and highly alkaliphilic bacterial strain (BKH4; GenBank accession no. KX622782) belonging to the family 'Bacillaceae' and homologous (99%) with Lysinibacillus fusiformis was isolated from Bakreshwar hot springs. The isolated coccoid-type Gram-positive bacterium grows well in a defined semi-synthetic medium (pH 12·0 and 65°C). This bacterium survives for more than a month and shows better efficacy in enhancing compressive strengths (>50%), ultrasonic pulse velocity (>25%) and durability of the cementitious mortar when incorporated at a concentration of 104  cells per ml of water used. CONCLUSION: The novel bacterium BKH4 is more effective for the enhancement of the bioconcrete properties. SIGNIFICANCE AND IMPACT OF THE STUDY: BKH4 bacterium will add a new dimension to future concrete technology for its usefulness in strength enhancement and durability due to its alkaliphilic nature and longer survival within a cementitious environment.

Genomic comparison of facultatively anaerobic and obligatory aerobic Caldibacillus debilis strains GB1 and Tf helps explain physiological differences.

Caldibacillus debilis strains GB1 and Tf display distinct phenotypes. Caldibacillus debilis GB1 is capable of anaerobic growth and can synthesize ethanol while C. debilis Tf cannot. Comparison of the GB1 and Tf genome sequences revealed that the genomes were highly similar in gene content and showed a high level of synteny. At the genome scale, there were several large sections of DNA that appeared to be from lateral gene transfer into the GB1 genome. Tf did have unique genetic content but at a much smaller scale: 300 genes in Tf verses 857 genes in GB1 that matched at ≤90% sequence similarity. Gene complement and copy number of genes for the glycolysis, tricarboxylic acid cycle, and electron transport chain pathways were identical in both strains. While Tf is an obligate aerobe, it possesses the gene complement for an anaerobic lifestyle (ldh, ak, pta, adhE, pfl). As a species, other strains of C. debilis should be expected to have the potential for anaerobic growth. Assaying the whole cell lysate for alcohol dehydrogenase activity revealed an approximately 2-fold increase in the enzymatic activity in GB1 when compared with Tf.

Two selenium tolerant Lysinibacillus sp. strains are capable of reducing selenite to elemental Se efficiently under aerobic conditions.

Microbes play important roles in the transport and transformation of selenium (Se) in the environment, thereby influencing plant resistance to Se and Se accumulation in plant. The objectives are to characterize the bacteria with high Se tolerance and reduction capacity and explore the significance of microbial origins on their Se tolerance, reduction rate and efficiency. Two bacterial strains were isolated from a naturally occurred Se-rich soil at tea orchard in southern Anhui Province, China. The reduction kinetics of selenite was investigated and the reducing product was characterized using scanning electron microscopy and transmission electron microscopy-energy dispersive spectroscopy. The bacteria were identified as Lysinibacillus xylanilyticus and Lysinibacillus macrolides, respectively, using morphological, physiological and molecular methods. The results showed that the minimal inhibitory concentrations (MICs) of selenite for L. xylanilyticus and L. macrolides were 120 and 220 mmol/L, respectively, while MICs of selenate for L. xylanilyticus and L. macrolides were 800 and 700 mmol/L, respectively. Both strains aerobically reduced selenite with an initial concentration of 1.0 mmol/L to elemental Se nanoparticles (SeNPs) completely within 36 hr. Biogenic SeNPs were observed both inside and outside the cells suggesting either an intra- or extracellular reduction process. Our study implied that the microbes from Se-rich environments were more tolerant to Se and generally quicker and more efficient than those from Se-free habitats in the reduction of Se oxyanions. The bacterial strains with high Se reduction capacity and the biological synthesized SeNPs would have potential applications in agriculture, food, environment and medicine.

Genome sequence and description of Gracilibacillus timonensis sp. nov. strain Marseille-P2481T , a moderate halophilic bacterium isolated from the human gut microflora.

Microbial culturomics represents an ongoing revolution in the characterization of the human gut microbiota. By using three culture media containing high salt concentrations (10, 15, and 20% [w/v] NaCl), we attempted an exhaustive exploration of the halophilic microbial diversity of the human gut and isolated strain Marseille-P2481 (= CSUR P2481 =  DSM 103076), a new moderately halophilic bacterium. This bacterium is a Gram-positive, strictly aerobic, spore-forming rod that is motile by use of a flagellum and exhibits catalase, but not oxidase activity. Strain Marseille-P2481 was cultivated in media containing up to 20% (w/v) NaCl, with optimal growth being obtained at 37°C, pH 7.0-8.0, and 7.5% [w/v] NaCl). The major fatty acids were 12-methyl-tetradecanoic acid and hexadecanoic acid. Its draft genome is 4,548,390 bp long, composed of 11 scaffolds, with a G+C content of 39.8%. It contains 4,335 predicted genes (4,266 protein coding including 89 pseudogenes and 69 RNA genes). Strain Marseille-P2481 showed 96.57% 16S rRNA sequence similarity with Gracilibacillus alcaliphilus strain SG103T , the phylogenetically closest species with standing in nomenclature. On the basis of its specific features, strain Marseille-P2481T was classified as type strain of a new species within the genus Gracilibacillus for which the name Gracilibacillus timonensis sp. nov. is formally proposed.

Functional Characterization of Probiotic Potential of Novel Pigmented Bacterial Strains for Aquaculture Applications.

The bioprospecting proficient of novel pigmented probiotic strains with respect to aquaculture industry was unexplored hitherto. In this study, we investigated the probiotic potential of novel pigmented bacterial strains isolated from the indigenous soil sediments in their vicinal habitats, which were screened for their antimicrobial activity against aquatic pathogens using agar well diffusion assay. The strains namely Exiguobacterium acetylicum (S01), Aeromonas veronii (V03), and Chryseobacterium joostei (V04) were phenotypically identified and confirmed by 16S rRNA gene sequence analysis. Further characterization revealed that strains S01 and V03 survive relatively in lower pH and higher bile salt concentrations and possess good adherence ability and broad-spectrum antibiotic susceptibility. The isolate S01 exhibited the higher adhesion ability to hydrocarbons (82%) and mannose-specific adhesion (msa) gene expression. Additionally, the probiotic effects were evaluated in Artemia nauplii fed with algae supplemented with S01, V03, and V04 strains (2.7 × 107 cfu/mL) for 3 days under axenic environment. We observed a significant increase (p < 0.05) in the survival rate of Artemia nauplii treated with S01 (83 ± 5%) and V03 (55 ± 5%), whereas the survival rate was only 30 ± 0% in the untreated group. Moreover, the individual length (IL) was increased in treated group S01 (156.7 ± 2.2 µm), V03 (146.1 ± 3.4 µm), and V04 (134.4 ± 2.5 µm) compared with untreated group (116.0 ± 4.8 µm). Our results revealed that E. acetylicum S01 exhibits desirable functional probiotic attributes compared to A. veronii and C. joostei and it would be a promising probiotic strain, which can be efficiently used in the aquaculture applications.

The whole genome insight on condition-specific redox activity and arsenopyrite interaction promoting As-mobilization by strain Lysinibacillus sp. B2A1.

A gram-positive spore former, Lysinibacillus sp. B2A1 was isolated from a high arsenic containing groundwater of Beimen2A well, Chianan Plain area, Southwestern Taiwan. Noteworthy, in the subsurface-mimicking anoxic incubation with a Na-lactate amendment system, this isolate could interact with arsenic-source mineral arsenopyrite and enhance arsenic mobilization. Further, the isolate showed elevated levels of arsenic resistance, 200 mM and 7.5 mM for arsenate and arsenite, respectively. Lysinibacillus sp. B2A1 demonstrated condition-specific redox activities including salient oxic oxidation of arsenite and anoxic reduction of arsenate. The elevated rate of As(III) oxidation (Vmax = 0.13 µM min-1 per 106 cells, Km = 15.3 µM) under oxic conditions was potent. Correlating with stout persistence in an arsenic-rich niche, remarkably, the lesser toxic effects of arsenic ions on bacterial sporulation frequency and germination highlight this strain's ability to thrive under catastrophic conditions. Moreover, the whole genome analysis elucidated diverse metal redox/resistance genes that included a potential arsenite S-adenosylmethyltransferase capable of mitigating arsenite toxicity. Owing to its arsenic resistance, conditional redox activities and ability to interact with arsenic minerals leading to arsenic mobilization, the presence of such spore-forming strains could be a decisive indication towards arsenic mobilization in subsurface aquifers having a high concentration of soluble arsenic or its source minerals.

Cell-gel interactions of in-gel propagating bacteria.

OBJECTIVE: Our immediate objective is to test the data-suggested possibility that in-agarose gel bacterial propagation causes gel fiber dislocation and alteration of cell distribution. We also test the further effect of lowering water activity. We perform these tests with both Gram-negative and Gram-positive bacteria. Data are obtained via electron microscopy of thin sections, which provides the first images of both bacteria and gel fibers in gel-supported bacterial lawns. The long-term objective is analysis of the effects of in-gel propagation on the DNA packaging of phages. RESULTS: We find that agarose gel-supported cells in lawns of Escherichia coli and Lysinibacillus (1) are primarily in clusters that increase in size with time and are surrounded by gel fibers, and (2) sometimes undergo gel-induced, post-duplication rotation and translation. Bacterial growth-induced dislocation of gel fibers is observed. One reason for clustering is that clustering promotes growth by increasing the growth-derived force applied to the gel fibers. Reactive force exerted by gel on cells explains cell movement. Finally, addition to growth medium of 0.94 M sucrose causes cluster-associated E. coli cells to become more densely packed and polymorphic. Shape is determined, in part, by neighboring cells, a novel observation to our knowledge.

Salicibibacter kimchii gen. nov., sp. nov., a moderately halophilic and alkalitolerant bacterium in the family Bacillaceae, isolated from kimchi.

A moderately halophilic and alkalitolerant bacterial strain NKC1-1T was isolated from commercial kimchi in Korea. Strain NKC1-1T was Gram-stain-positive, aerobic, rod-shaped, non-motile, and contained diaminopimelic acid-type murein. Cell growth was observed in a medium containing 0-25% (w/v) NaCl (optimal at 10% [w/v]), at 20-40°C (optimal at 37°C) and pH 6.5-10.0 (optimal at pH 9.0). The major isoprenoid quinone of the isolate was menaquinone-7, and the major polar lipids were phosphatidylglycerol and unidentified phospholipids. Cell membrane of the strain contained iso-C17:0 and anteiso-C15:0 as the major fatty acids. Its DNA G + C content was 45.2 mol%. Phylogenetic analysis indicated the strain to be most closely related to Geomicrobium halophilum with 92.7-92.9% 16S rRNA gene sequence similarity. Based on polyphasic taxonomic evaluation with phenotypic, phylogenetic, and chemotaxonomic analyses, the strain represents a novel species in a new genus, for which the name Salicibibacter kimchii gen. nov., sp. nov. is proposed (= CECT 9537T; KCCM 43276T).

Functional annotation of hypothetical proteins from the Exiguobacterium antarcticum strain B7 reveals proteins involved in adaptation to extreme environments, including high arsenic resistance.

Exiguobacterium antarcticum strain B7 is a psychrophilic Gram-positive bacterium that possesses enzymes that can be used for several biotechnological applications. However, many proteins from its genome are considered hypothetical proteins (HPs). These functionally unknown proteins may indicate important functions regarding the biological role of this bacterium, and the use of bioinformatics tools can assist in the biological understanding of this organism through functional annotation analysis. Thus, our study aimed to assign functions to proteins previously described as HPs, present in the genome of E. antarcticum B7. We used an extensive in silico workflow combining several bioinformatics tools for function annotation, sub-cellular localization and physicochemical characterization, three-dimensional structure determination, and protein-protein interactions. This genome contains 2772 genes, of which 765 CDS were annotated as HPs. The amino acid sequences of all HPs were submitted to our workflow and we successfully attributed function to 132 HPs. We identified 11 proteins that play important roles in the mechanisms of adaptation to adverse environments, such as flagellar biosynthesis, biofilm formation, carotenoids biosynthesis, and others. In addition, three predicted HPs are possibly related to arsenic tolerance. Through an in vitro assay, we verified that E. antarcticum B7 can grow at high concentrations of this metal. The approach used was important to precisely assign function to proteins from diverse classes and to infer relationships with proteins with functions already described in the literature. This approach aims to produce a better understanding of the mechanism by which this bacterium adapts to extreme environments and to the finding of targets with biotechnological interest.

Effects of plant- and animal-based high-fat diets on lipid storage and distribution in environmental bacteria-colonized gnotobiotic mice.

Different edible oils such as lard and soybean oil have been reported to interact with the gut microbiota, affecting host lipid metabolism. However, whether bacteria derived from the environment influence host lipid metabolism remains unclear. This study aimed to clarify the roles of environmental bacteria in host lipid storage and distribution with various edible oils. Gnotobiotic C57BL/6JNarl mice were inoculated with Lysinibacillus xylanilyticus and Paenibacillus azoreducens and then fed either a normal diet (LabDiet 5010, control group) or a diet containing 60% lard (L-group) or soybean oil (S-group) for 18 months. Interestingly, the S-group accumulated massive amounts of white adipose tissue compared to the L- and control groups, while the L-group displayed more hepatic steatosis and fatty droplets than the other groups. The expression of fatty acid synthase (FAS), hydroxymethylglutaryl-coenzyme A reductase (HMGCR), sterol regulatory element-binding protein 2 (SREBP2), and peroxisome proliferator-activated receptor gamma (PPARγ) in the livers of the L-group were markedly elevated compared to the S-group. FAS and PPARγ protein levels were also markedly elevated. However, there were no differences in the expression of the pro-inflammatory cytokines interleukin-6 and tumor necrosis factor-α between the groups. Our results suggest that environmental bacteria may affect host hepatic inflammation and lipid distribution in the presence of high-fat diets, with different effects depending on the fat type consumed.

Determination of the biofilm production capacities and characteristics of members belonging to Bacillaceae family.

The biofilm characteristics of many endospore-forming bacilli, especially the thermophiles are still unclear. In this study, a detailed identification and description of biofilm production characteristics of totally 145 isolates and reference strains belonging to Bacillaceae family, displaying thermophilic (n = 115), facultative thermophilic (n = 24) and mesophilic (n = 6) growth from genera Anoxybacillus, Geobacillus, Thermolongibacillus, Aeribacillus, Brevibacillus, Paenibacillus and Bacillus were presented. The incubation temperatures were adjusted to 37, 45 and 55-65 °C for mesophiles, facultative thermophiles, and thermophiles, respectively. The bacilli were evaluated based on their colony morphotypes on Congo red (CR) agar, their complex exopolysaccharide production on calcofluor supplemented tryptic soy agar, and as well as their pellicle formation at the liquid-air surface in tryptic soy broth cultures. Their biofilm production capabilities were also tested on abiotic surfaces of both polystyrene and stainless steel by crystal violet binding assay and viable biofilm cell enumerations, respectively. As a result, the biofilm production capacities of Bacillaceae members from genera to species level, the effects of osmolarity, temperature, incubation time and abiotic surfaces on biofilm formation as well as the CR morphotypes associated with the biofilm production were able to reveal in a wide group of bacilli. Besides, general enrichment-inoculation approaches and methodologies were also offered, which allow and facilitate the screening and determining the biofilm producing endospore forming bacilli.