PCR screening reveals abundance of bovicin-like bacteriocins among ruminal Streptococcus spp. isolated from beef and dairy cattle.

AIMS: To investigate the inhibitory activity and the distribution of biosynthetic genes encoding bovicin-like bacteriocins among ruminal Streptococcus isolated from beef and dairy cattle. METHODS AND RESULTS: Most isolates were classified as Streptococcus equinus and Streptococcus lutetiensis based on 16S rRNA sequencing. The antimicrobial activity of 150 ruminal streptococci isolated from beef and dairy cattle were tested by deferred inhibition assays and their genetic diversity was characterized by BOX-PCR. The frequency of biosynthetic genes associated with the biosynthesis of bovicin-like bacteriocins (bovicin HC5 and bovicin 255) was investigated by PCR screening. Approximately 33% of the ruminal streptococci isolated from Nellore heifers showed inhibitory activity in vitro with the majority harbouring genes for bacteriocin biosynthesis. In contrast, streptococci from Holstein cows showed limited inhibitory activity and a lower frequency of bacteriocin biosynthetic genes. CONCLUSIONS: Streptococcus from the rumen of beef and dairy cattle exhibit remarkable differences in inhibitory activity and distribution of genes associated with the biosynthesis of prototypical bovicins (bovicin HC5 and bovicin 255). SIGNIFICANCE AND IMPACT OF THE STUDY: Our findings demonstrate that bovicin HC5 is distributed among ruminal streptococci from different breeds of cattle. The high degree of conservation of the bovicin HC5 structural gene among strains of ruminal streptococci suggests that random genetic drift is not a dominant force in the evolution of this bacteriocin.

Differential expression of plg genes from Penicillium griseoroseum: plg1 a pectinolytic gene is expressed in sucrose and yeast extract.

AIMS: To study the regulation of the plg1 and plg2 genes of Penicillium griseoroseum, in order to identify the industrial potential of their products in alternative carbon sources that are cheaper and widely available in Brazil. METHODS AND RESULTS: RT-PCR and Northern blot were used to investigate if plg1 and plg2 expression is under influence of catabolic repression, ambient pH and cAMP. Results demonstrated that the genes were differentially regulated depending on the carbon sources in the culture medium and pH. Sucrose, a noninducing carbon source of the pectinolytic system, was able to promote plg1 transcription but only when yeast extract was added into the culture medium. CONCLUSIONS: The plg genes are differentially expressed. The plg1 gene is more attractive for industrial use due to its expression in alternative carbon sources like sucrose and yeast extract. SIGNIFICANCE AND IMPACT OF THE STUDY: In recent years, industries have been trying to replace the toxic conventional treatments employed in these processes by more eco-friendly enzyme treatment. Alternative carbon sources will be tested with the aim to reduce the costs associated to pectin lyase production in Brazil.