Phylogenetic diversity of aerobic spore-forming Bacillalles isolated from Brazilian soils

Characterization by MALDI-TOF MS and 16S rRNA Gene Sequencing of Aerobic Endospore-Forming Bacteria Isolated from Pharmaceutical Facility in Rio de Janeiro, Brazil

Bacillus and related genera are among the most important contaminants in the pharmaceutical production environment, and the identification of these microorganisms at the species level assists in the investigation of sources of contamination and in preventive and corrective decision making. The aim of this study was to evaluate three methodologies for the characterization of endospore-forming aerobic bacterial strains isolated from a pharmaceutical unit in Rio de Janeiro, Brazil. MALDI-TOF MS was performed using MALDI Biotyper® and VITEK® MS RUO systems, and complete 16S rRNA gene sequencing was performed using the Sanger methodology. The results showed the prevalence of the genera Bacillus (n = 9; 36.0%), Priestia (n = 5; 20.0%), and Paenibacillus (n = 4; 16.0%). Three (20.0%) strains showed <98.7% of DNA sequencing similarity on the EzBioCloud Database, indicating possible new species. In addition, the reclassification of Bacillus pseudoflexus to the genus Priestia as Priestia pseudoflexus sp. nov. is proposed. In conclusion, 16S rRNA and MALDI TOF/MS were not sufficient to identify all strains at the species level, and complementary analyses were necessary.

Grazing practices affect soil microbial networks but not diversity and composition in alpine meadows of northeastern Qinghai-Tibetan plateau

Livestock grazing is the primary practice in alpine meadows and can alter soil microbiomes, which is critical for ecosystem functions and services. Seasonal grazing (SG) and continuous grazing (CG) are two kinds of different grazing practices that dominate alpine meadows on the Qinghai-Tibetan Plateau (QTP), and how they affect soil microbial communities remains in-depth exploration. The present study was conducted to investigate the effects of different grazing practices (i.e., SG and CG) on the diversity, composition, and co-occurrence networks of soil bacteria and fungi in QTP alpine meadows. Soil microbial α- and β-diversity showed no obvious difference between SG and CG grasslands. Grazing practices had little impact on soil microbial composition, except that the relative abundance of Proteobacteria and Ascomycota showed significant difference between SG and CG grasslands. Soil microbial networks were more complex and less stable in SG grasslands than that in CG grasslands, and the bacterial networks were more complex than fungal networks. Soil fungal diversity was more strongly correlated with environmental factors than bacteria, whereas both fungal and bacterial structures were mainly influenced by soil pH, total nitrogen, and ammonium nitrogen. These findings indicate that microbial associations are more sensitive to grazing practices than microbial diversity and composition, and that SG may be a better grazing practice for ecological benefits in alpine meadows.

Biochemical, physiological, and molecular characterisation of a large collection of aerobic endospore-forming bacteria isolated from Brazilian soils

The aerobic endospore-forming bacteria (AEFB) comprise species of Bacillus and related genera and have long been regarded as prominent constituents of the soil bacterial community. The wide diversity of AEFB renders appropriate categorisation and generalisations a challenging task. We previously isolated 312 AEFB strains from Brazilian soils that we designated SDF (Solo do Distrito Federal) strains. To better understand the SDF diversity and explore their biotechnological potential, we addressed the biochemical and physiological profiles of these 312 environmental strains by performing 30 tests in this work. Of these, the 16S rRNA gene sequences segregated 238 SDF strains into four genera in the family Bacillaceae and two in the Paenibacillaceae. Bacillus spp. were the most prevalent, followed by species of Paenibacillus. We summarised the phenotypic test relationships among selected SDF strains using a Pearson correlation-based clustering represented in heatmaps. In practice, biochemical and physiological profiles are often less discriminatory than molecular data and may be unstable because of the loss of traits. Although these test reactions are not universally positive or negative within species, they may define biotypes and be efficient strain markers, enhancing the accuracy of unknown sample identification. It can also help select the most representative phenotypes of samples. Along with the other phenotypic and genotypic data, the present results are of great importance for the robust classification of the SDF strains within the scope of the polyphasic approach.

Oral administration of Bacillus cereus GW-01 alleviates the accumulation and detrimental effects of β-cypermethrin in mice

Pyrethroid insecticides negatively affect feed conversion, reproductive fitness, and food safety in exposed animals. Although probiotics have previously been widely studied for their effect on gut health, comparatively little is known regarding the efficacy of probiotic administration in specifically reducing pesticide toxicity in mice. We demonstrated that oral administration of a β-cypermethrin (β-CY)-degrading bacterial strain (Bacillus cereus GW-01) to β-CY-exposed mice reduced β-CY levels in the liver, kidney, brain, blood, lipid, and feces (18%-53%). Additionally, co-administration of strain GW-01 to β-CY-exposed mice reduced weight loss (22%-31%) and improved liver function (15%-19%) in mice. Additionally, mice receiving GW-01 had near-control levels of numerous β-CY-affected gut microbial taxa, including Muribaculaceae, Alloprevotella, Bacteroides, Dubosiella, and Alistipes. The survival and β-CY biosorption of GW-01 in simulated gastrointestinal fluid conditions were significantly higher than E. coli. These results suggested that GW-01 can reduce β-CY accumulation and alleviate the damage in mice. This study is the first to demonstrate that a probiotic strain can reduce the toxicity of β-CY in mice.