For these experiments, in order to obtain sufficient RNA for analysis, the zoocin A and PS-ODNs were added to cultures in log phase growth (as opposed to stationary phase) and at a higher cell density than other
experiments. It was found that use of zoocin A at 0.4 μg mL−1 in these experiments (as opposed to 0.1 μg mL−1, Table 1), resulted in a comparable increase in lag phase to that seen in previous experiments. There were no significant differences (P=0.05) in the transcript levels for either the 16sRNA or gyrA controls in any sample. This shows that the growth inhibition observed in zoocin A- and FBA-treated cultures (Fig. 2) did not result from the induction of a nonspecific ribonuclease. Natural Product Library Compared with cultures treated with either zoocin A or FBA alone, a significant decrease (P=0.001) in expression of fba was observed at both 30 min (1067.86-fold) and 5 h (2509.16-fold) in cultures treated with zoocin A and FBA. Growth of the culture resumed 4 h after the addition of zoocin A and FBA (Fig. 2), and no significant difference (P=0.05) in values were observed for fba expression levels at times 0 or 16 h, or at any time for any other treatment Trichostatin A regime. The drastic reduction in the expression of fba in FBA-treated S. mutans cells was both gene and PS-ODN specific, confirming that the phenotypic
loss of viability observed did not occur as a result of nonspecific cellular toxicity by FBA. Cellular uptake of exogenously added asODNs would facilitate the study of gene function in prokaryotic organisms. In conclusion, this work demonstrated that the bacteriolytic enzyme zoocin
A, used Cyclin-dependent kinase 3 at a sublethal concentration, was successful in facilitating the entry of PS-ODNs into streptococcal cells. The degree of inhibition of cell growth, measured as increased lag-phase, was target specific and sensitive to the amount of both zoocin A and PS-ODN used. This work was undertaken with support from the Foundation for Research Science and Technology. “
“The bacterial diversity of seeds, transmission of bacteria from seed to phyllosphere, and fate of seed-transmitted bacteria on mature plants are poorly characterized. Understanding the dynamics of microbial communities is important for finding bio-control or mitigation strategies for human and plant pathogens. Bacterial populations colonizing spermosphere and phyllosphere of spinach (Spinacia oleracea) seedlings and plants were characterized using pyrosequencing of 16S rRNA gene amplicons. Spinach seed microbiota was composed of three bacterial phyla: Proteobacteria, Firmicutes and Actinobacteria, belonging to > 250 different operational taxonomic units (OTUs). Seed and cotyledon bacterial communities were similar in richness and diversity.