AUTHOR=Berendsen Erwin M. , Koning Rosella A. , Boekhorst Jos , de Jong Anne , Kuipers Oscar P. , Wells-Bennik Marjon H. J. 

TITLE=High-Level Heat Resistance of Spores of Bacillus amyloliquefaciens and Bacillus licheniformis Results from the Presence of a spoVA Operon in a Tn1546 Transposon

JOURNAL=Frontiers in Microbiology

VOLUME=7

YEAR=2016

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2016.01912

DOI=10.3389/fmicb.2016.01912

ISSN=1664-302X

ABSTRACT=<p>Bacterial endospore formers can produce spores that are resistant to many food processing conditions, including heat. Some spores may survive heating processes aimed at production of commercially sterile foods. Recently, it was shown that a <italic>spoVA</italic> operon, designated <italic>spoVA</italic><sup>2mob</sup>, present on a Tn<italic>1546</italic> transposon in <italic>Bacillus subtilis</italic>, leads to profoundly increased wet heat resistance of <italic>B. subtilis</italic> spores. Such Tn<italic>1546</italic> transposon elements including the <italic>spoVA</italic><sup>2mob</sup> operon were also found in several strains of <italic>Bacillus amyloliquefaciens</italic> and <italic>Bacillus licheniformis</italic>, and these strains were shown to produce spores with significantly higher resistances to wet heat than their counterparts lacking this transposon. In this study, the locations and compositions of Tn<italic>1546</italic> transposons encompassing the <italic>spoVA</italic><sup>2mob</sup> operons in <italic>B. amyloliquefaciens</italic> and <italic>B. licheniformis</italic> were analyzed. Introduction of these <italic>spoVA</italic><sup>2mob</sup> operons into <italic>B. subtilis</italic> 168 (producing spores that are not highly heat resistant) rendered mutant 168 strains that produced high-level heat resistant spores, demonstrating that these elements in <italic>B. amyloliquefaciens</italic> and <italic>B. licheniformis</italic> are responsible for high level heat resistance of spores. Assessment of growth of the nine strains of each species between 5.2°C and 57.7°C showed some differences between strains, especially at lower temperatures, but all strains were able to grow at 57.7°C. Strains of <italic>B. amyloliquefaciens</italic> and <italic>B. licheniformis</italic> that contain the Tn<italic>1546</italic> elements (and produce high-level heat resistant spores) grew at temperatures similar to those of their Tn<italic>1546</italic>-negative counterparts that produce low-level heat resistant spores. The findings presented in this study allow for detection of <italic>B. amyloliquefaciens</italic> and <italic>B. licheniformis</italic> strains that produce highly heat resistant spores in the food chain.</p>