Relative Expression of Germination Genes SleB, GerAC, and Gpr in Heat Treated Bacillus licheniformis and Bacillus subtilis

<p>Endospore-forming bacteria of the genus <em>Bacillus</em> are of significant importance to the food industry. Species from this genus exhibit the ability to form metabolically dormant endospores characterized by resistance to heat, UV, and chemical treatment. Spores have undetectable metabolic activity and remain impervious to the harsh conditions of their environment, but they can detect environmental cues signaling favorable growth conditions and begin the process of germination. Once germination and outgrowth are complete, the fully viable cell is capable of reproducing and forming colonies. The resistance of these endospores has been a topic of decades of research, particularly because of their impact on food processing. Only a few species of <em>Bacillus</em> are actually pathogenic, but many others present quality defects, particularly in milk and other dairy products.</p> <p>This study involved the selection and use of primers specific for GerAC, <em>gpr</em>, and <em>SleB</em> genes to evaluate their relative expression and potential for indicators of lag phase in germination. Gene expression studies with qPCR were carried out during germination in <em>Bacillus subtilis </em>and <em>Bacillus licheniformis</em> spores that were given a heat shock in a tryptic soy broth at 80°C and subsequently incubated for 0, 30, 60, and 120 minutes at their optimal growth temperatures. Expression ratios calculated relative to the samples incubated for 120min (R=1) showed increased expression as germination and outgrowth progressed (GerAC gene on <em>B. licheniformis </em>and <em>B. subtilis</em>; R_30min=0.14 and 0.14, R_60min=0.76 and 0.51)_.<em> </em>The different expression levels measured in this preliminary study suggest that the selected genes and methodology merit further optimization to verify the accuracy and significance of the assay as well as its application it to the milk powder process.</p>

Name thesis:degree_name

MS in Agriculture - Dairy Products Technology

Discipline thesis:degree_discipline

Dairy Science

Year dc:date.available

2014

Author dc:creator

• Arechiga, Valerie Paige

Contributors dc:contributor

• Rafael Jimenez-Flores

Identifier

10.15368/theses.2014.190

OAI identifier oai:identifier

oai:digitalcommons.calpoly.edu:theses-2430