Effect of pH and Carbon Source on Phosphate Solubilization by Bacterial Strains in Pikovskaya Medium.

Phosphate-solubilizing bacteria (PSB) transform precipitated inorganic phosphorus into soluble orthophosphates. This study evaluated the efficiency of tricalcium and iron phosphate solubilization in Pikovskaya medium using five bacterial strains (A1, A2, A3, A5, and A6) cultured in acidic and alkaline pH levels. The bacterial strain that proved to be more efficient for P solubilization and was tolerant to pH variations was selected for assessing bacterial growth and P solubilization with glucose and sucrose in the culture medium. The bacterial strains were identified through 16S rRNA gene sequencing as Pseudomonas libanensis A1, Pseudomonas libanensis (A2), Bacillus pumilus (A3), Pseudomonas libanensis (A5), and Bacillus siamensis (A6). These five bacterial strains grew, tolerated pH changes, and solubilized inorganic phosphorus. The bacterial strain A3 solubilized FePO4 (4 mg L-1) and Ca3(PO4)2 (50 mg L-1). P solubilization was assayed with glucose and sucrose as carbon sources for A3 (Bacillus pumilus MN100586). After four culture days, Ca3(PO4)2 was solubilized, reaching 246 mg L-1 with sucrose in culture media. Using glucose as a carbon source, FePO4 was solubilized and reached 282 mg L-1 in six culture days. Our findings were: Pseudomonas libanensis, and Bacillus siamensis, as new bacteria, can be reported as P solubilizers with tolerance to acidic or alkaline pH levels. The bacterial strain B. pumilus grew using two sources of inorganic phosphorus and carbon, and it tolerated pH changes. For that reason, it is an ideal candidate for inorganic phosphorus solubilization and future production as a biofertilizer.

Aplicar o no aplicar un procedimiento médico: esa es la cuestión / To perform or not to perform a medical procedure: that is the question

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Prevalence of pathogens associated with bovine mastitis in bulk tank milk in Mexico.

Mastitis as cause of low milk production coupled with the use of medication to control it cause dairy farms to register large economic losses. Microorganisms' prevalence, and somatic cell counts (SCCs) were determined in 112 Holstein bovine herds in two bulk tank milk-screening assays. Detection of Staphylococcus aureus, Streptococcus agalactiae, and Mycoplasma spp. as microorganisms primarily responsible for clinical and subclinical mastitis and their relationship with SCCs was evaluated by Student's t-test and the kappa test. Prevalence of Mycoplasma was 55%; of S. aureus, 30%; of Streptococcus uberis, 37.5%; and of Staphylococcus coagulase-negative, 38.3%. The geometric mean of the SCC was 465,000 cells/mL. No significant differences were observed in the SCCs between the positive and negative samples of pathogens isolated (P > 0.5). There was a low kappa value of Mycoplasma correlation between samplings (kappa value = 0.10). This work aimed to understand the relationship between the prevalence of mastitis pathogens in bulk tank milk and SCCs in bovine herds in the central part of Mexico.