Aim: We sought to confirm the presence of halophilic and alkaliphilic lactic acid bacteria (HALAB) of marine origin in cheeses and thus contribute to the understanding of the roles of LAB flora in cheese ripening.
Methods and Results: We used 7% NaCl glucose–yeast extract–peptone–fish extract broth and agar media (pH 9·5) for pour‐plating and enrichment culture for 16 cheese samples produced in six European countries. HALAB were present in 9 of the 16 samples at <20–>107 CFU g−1. In three mould‐ripened soft cheeses, HALAB counts ranged from 106 to 107 CFU g−1 and were one order (two samples) and six orders (one sample) of magnitude greater than that of nonhaloalkaliphilic, common LAB, as enumerated on lactobacilli MRS agar. The 16S rRNA gene sequences (500 bp) of 51 of the 55 isolates examined were identical or similar to that of Marinilactibacillus psychrotolerans or Alkalibacterium olivapovliticus and related species, all of which are HALAB.
Conclusions: HALAB of possible marine origin were present in various soft, semi‐hard and semi‐soft cheeses and were highly predominant in some mould‐ripened cheeses.
Significance and Impact of the Study: HALAB of possible marine origin are members of the microflora of various cheeses and, when dominant, may play a role in the ripening of cheeses. Microbial analysis of LAB flora in cheeses should take into consideration the presence of HALAB.
The groESL operon of Acetobacter aceti was cloned and sequenced. We observed that GroES and GroEL of A. aceti had high amino acid sequence homologies to GroES and GroEL of Escherichia coli and Bacillus subtilis. The upstream region of the groESL operon contained the heat-shock promoter, which was previously reported in alpha-purple proteobacteria, and the highly conserved inverted repeat sequence. Phylogenetic analysis revealed that the A. aceti GroES and GroEL are very closely related to those of other alpha-purple proteobacteria. Transcription of this operon in A. aceti was induced by heat shock as well as by exposure to ethanol and acetic acid, which are present during fermentation of acetic acid. A. aceti that overexpressed the groESL was more resistant than the control strain to Stressors such as heat, ethanol, or acetic acid, indicating that GroES and GroEL are closely associated with the characteristic nature of Acetobacter and play an important role in acetic acid fermentation.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.