Biology

Gram-positve Bacillus species are recognized as the most common microbiological organisms that contaminate milk (Torkar  Mozina 2000).  A number of methods have earlier been designed to prevent possible contamination of milk products before these are packaged and sent out for distribution to the market.  Methods such as pasteurization, as well as sterilization, have been extensively used by the dairy industry, yet there are still certain bacterial spores that could withstand such processes.  This investigation was conducted to determine the effect of specific treatments to the activation of Bacillus spores.  Briefly, spores of two Bacillus species (subtilis and cereus) were prepared from bacterial cultures through heat inactivation of vegetative cells.  The spores were then tested through different conditions involving heat, the presence of L-alanine and peptidoglycan.

The exposure of B. subtilis spores to heat showed a higher percentage of germination (-33 -6 Mean  -19.5) as compared to the control setup that was not subjected to heat (-42 -2.5 Mean  -22.25).  On the other hand, the exposure of B. cereus spores to heat resulted in an average of 50 rate in germination, while spores that were not subjected to heat activation was observed to have an average of 50 rate of germination.  Treatment of B. subtilis spores with L-alanine showed an average of 10 germination, while the control group resulted in an average of -7 rate of germination.  The treatment of B. cereus spores with L-alanine, on the other hand, resulted in an average of 21 germination, while the control setup resulted in an average of 52 germination.  The addition of peptidoglycan to the bacterial cultures also showed promising results, wherein treated B. subtilis spores showed an average of -33 germination, while the control B. subtilis spores resulted in an average of -25.5 germination.  In the case of B. cereus, the addition of peptidoglycan generated an -8 rate of germination, while the control spores showed an average of -81 rate of germination.

The results observed from this investigation showed that the activation of Bacillus spores could be influenced by the varying treatment conditions.  The results of heat treatment in both Bacillus species did not show any significant differences in the rate of germination.  The introduction of L-alanine to the Bacillus spores showed an increase in germination, suggesting that this process may be prevented through the regulation of the amount of this amino acid in the diary processing setup.  The administration of peptidoglycan to the spores showed opposite results in each species, wherein B. subtilis showed an activation of germination, while B. cereus resulted in a deactivation of germination.  The conditions described in this study may provide a better understanding of the mechanism of germination of Bacillus spores.  More importantly, the conditions presented in this study may be employed in dairy processing centers to generate safer milk products.