Curing experiments were performed onLactobacillus helveticus strain ATCC 15009 in order to find a correlation between the presence of three extrachromosomal elements and specific phenotypic traits. Mitomycin C treatment of the strain was found to result in an appearance of slow-coagulation variants unable to coagulate milk in 24 h at 42 °C. The effect of mitomycin C on phenotypic and genotypic characteristics ofL. helveticus was therefore further examined. The presence of mitomycin C appeared to act on the proteolytic system of the strain: slow variants exhibited a poor casein breakdown (50 % less) compared with the parental strain. Aminopeptidase activity and lactose utilization were unaffected. The phenotypic variation is possibly due to a point mutation of genetic patrimony. No loss of plasmid DNA was detected after mitomycin C treatment and the restriction pattern of plasmid and chromosomal DNA of the variants, after digestion with several restriction endonucleases, was identical to that obtained for the parental strain.
|Titolo:||Slow milk coagulating variants of Lactobacillus helveticus|
FORTINA, MARIA GRAZIA (Primo)
PARINI, CARLO (Penultimo)
|Settore Scientifico Disciplinare:||Settore AGR/16 - Microbiologia Agraria|
|Data di pubblicazione:||1996|
|Digital Object Identifier (DOI):||10.1007/BF02816337|
|Appare nelle tipologie:||01 - Articolo su periodico|