No abstract

We previously reported that microRNA (miRNA) is present in human breast milk. Recently, other groups have reported that bovine milk also contains miRNA; however, these reports are few. We therefore investigated bovine milk miRNA using microarray and quantitative PCR analyses to identify the differences between colostrum and mature milk. The RNA concentration in a colostrum whey fraction was higher than that in a mature milk whey fraction. In total, 102 miRNA were detected in bovine milk by microarray analysis (100 in colostrum and 53 in mature milk; 51 were common to both). Among these miRNA, we selected several immune- and development-related miRNA, including miR-15b, miR-27b, miR-34a, miR-106b, miR-130a, miR-155, and miR-223. These miRNA were detected in bovine milk by quantitative PCR, and each of these miRNA was significantly more highly expressed in colostrum than in mature milk. We also confirmed the presence of some mRNA in bovine milk. Nevertheless, synthesized miRNA spiked in the raw milk whey were degraded, and naturally existing miRNA and mRNA in raw milk were resistant to acidic conditions and RNase treatment. The RNA molecules in milk were stable. We also detected miRNA and mRNA in infant formulas purchased from Japanese markets. It is still unknown whether milk-derived RNA molecules play biological roles in infants; however, if milk-derived RNA do show functions in infants, our data will help guide future studies.

A physiologically diverse range of Gram-positive and Gram-negative bacteria was found to be susceptible to inhibition and inactivation by lactoferricin B, a peptide produced by gastric pepsin digestion of bovine lactoferrin. The list of susceptible organisms includes Escherichia coli, Salmonella enteritidis, Klebsiella pneumoniae, Proteus vulgaris, Yersinia enterocolitica, Pseudomonas aeruginosa, Campylobacter jejuni, Staphylococcus aureus, Streptococcus mutans, Corynebacterium diphtheriae, Listeria monocytogenes and Clostridium perfringens. Concentrations of lactoferricin B required to cause complete inhibition of growth varied within the range of 0.3 to 150 micrograms/ml, depending on the strain and the culture medium used. The peptide showed activity against E. coli O111 over the range of pH 5.5 to 7.5 and was most effective under slightly alkaline conditions. Its antibacterial effectiveness was reduced in the presence of Na+, K+, Mg2+ or Ca2+ ions, or in the presence of various buffer salts. Lactoferricin B was lethal, causing a rapid loss of colony-forming capability in most of the species tested. Pseudomonas fluorescens, Enterococcus faecalis and Bifidobacterium bifidum strains were highly resistant to this peptide.