Tolerance Induction of Temperature and Starvation with Tricalcium Phosphate on Preservation and Sporulation in Bacillus amyloliquefaciens Detected by Flow Cytometry

Meat extract casein peptone agar - A novel culture medium for the enumeration of Bacillus endospores in commercial products

Here we propose a novel culture medium, Meat Extract Casein Peptone (MECP) agar, to support the enumeration of Bacillus endospores in commercial products. The formulation is the result of screening eight different veterinary, pharmaceutical, and industrial grade peptones for the ability to support the formation of small, well-defined Bacillus colonies on solid culture medium. The impact of agar purity, agar formulation rate, and metal cation additives were examined in prototype medium batches prepared from preferred peptone inputs. A customized plate counting assay based on the resultant MECP agar formulation was compared with standardized pour-plate and spread-plate assays (ISO 4833) and flow cytometry for the ability to accurately enumerate five Bacillus-based biostimulants and biofertilizers. Estimations of Bacillus endospore concentration generated by the customized spread-plate assay were significantly higher than those produced by ISO 4833 pour-plate and spread-plate assays for four out of the five tested products and were in better agreement with flow cytometry values; however, flow cytometry values were numerically higher than values returned by both plating methods. Both flow cytometry and plating assays based on MECP or similar culture media represent potential candidates for standardization and validation through organizations such as ISO and AOAC International for the enumeration of Bacillus-based products.

Metabolic and proteomic mechanism of bisphenol A degradation by Bacillus thuringiensis

Bisphenol A (BPA) is a worldwide, widespread pollutant with estrogen mimicking and hormone-like properties. To date, some target biomolecules associated with BPA toxicity have been confirmed. The limited information has not clarified the related metabolism at the pathway and network levels. To this end, metabolic and proteomic approaches were performed to reveal the synthesis of phospholipids and proteins and the metabolic network during the BPA degradation process. The results showed that the degradation efficiency of 1 μM of BPA by 1 g L^-1 of Bacillus thuringiensis was up to 85% after 24 h. During this process, BPA significantly changed the membrane permeability; altered sporulation, amino acid and protein expression, and carbon, purine, pyrimidine and fatty acid metabolism; enhanced C14:0, C16:1ω7, C18:2ω6, C18:1ω9t and C18:0 synthesis; and increased the trans/cis ratio of C18:1ω9t/C18:1ω9c. It also depressed the spore DNA stability of B. thuringiensis. Among the 14 upregulated and 7 down-regulated proteins, SasP-1 could be a biomarker to reflect BPA-triggered spore DNA impairment. TpiA, RpoA, GlnA and InfA could be phosphorylated at the active sites of serine and tyrosine. The findings presented novel insights into the interaction among BPA stress, BPA degradation, phospholipid synthesis and protein expression at the network and phylogenetic levels.