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Modified microassay for the isolation of antimicrobial‐producing, spore‐forming and nonspore‐forming bacteria
Author(s) -
Gerst M.M.,
Yousef A.E.
Publication year - 2018
Publication title -
journal of applied microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.889
H-Index - 156
eISSN - 1365-2672
pISSN - 1364-5072
DOI - 10.1111/jam.13724
Subject(s) - antimicrobial , bacteria , microbiology and biotechnology , listeria monocytogenes , biology , spore , bacillus (shape) , lysozyme , biochemistry , genetics
Aims To develop a microassay method to detect antimicrobials produced by spore‐forming bacteria, thus speeding up the discovery of new antimicrobials. Methods and Results Environmental isolates were grown in 96‐well plates, to allow production of antimicrobial agents, then treated with lysozyme and heated sequentially. Lysozyme heat treatment inhibited or prevented spore‐to‐cell transformation, thus eliminating interference from spore outgrowth while detecting antimicrobials by indicator bacteria. Supplementation of the indicator strain medium with 2,3,5‐triphenyltetrazolium chloride, as a vital stain, made it easy to rapidly differentiate between antimicrobial‐deficient (indicator growth) and antimicrobial‐containing (no growth) wells. The method was used to rapidly screen 657 bacteria isolated from eight soil samples. Results revealed 46 Bacillus sp. producing antimicrobials against Listeria sp., and a Bacillus sp. producing antimicrobial(s) against Escherichia coli . Conclusions A microassay method was successfully developed and implemented to screen and detect antimicrobial agents from spore‐forming, in addition to nonspore‐forming, bacteria. Significance and Impact of the Study Antimicrobials are needed to combat antibiotic‐ and preservative‐resistant bacteria. Spore‐forming bacteria are prolific producers of antimicrobials. This assay will speed the discovery of antimicrobials from spore‐forming bacteria; these new antimicrobials are urgently needed in food and medicinal applications.