Affiliation:
1. Department of Food Science, North Carolina State University, Raleigh, North Carolina 27695-7624
Abstract
Lactobacillus acidophilus
88 produced a bacteriocin, designated lactacin F, that demonstrated inhibitory activity toward
L. acidophilus
6032,
L. lactis
970,
L. helveticus
87,
L. bulgaricus
1489,
L. leichmanii
4797,
L. fermentum
1750, and
Streptococcus faecalis
19433. Production of lactacin F was pH dependent and could be maximized in MRS broth cultures maintained at pH 7.0. Lactacin F was heat stable and sensitive to ficin, proteinase K, trypsin, and
Bacillus subtilis
protease.
L. acidophilus
88 harbored plasmids of 4 and 27 megadaltons. Variants of
L. acidophilus
88 which were deficient in lactacin F production (Laf
+
) and lactacin F immunity (Laf
t
) retained the two resident plasmids. A Laf
−
Laf
s
derivative,
L. acidophilus
89, was used as a recipient in agar surface mating experiments with
L. acidophilus
88 (Laf
+
Laf
t
). Two types of Laf
+
Laf
t
transconjugants were recovered. One type (T-E) had acquired two plasmids of 68 (pPM68) and 52 (pPM52) megadaltons that were not detected in either the conjugal donor or the other type of Laf
+
Laf
t
transconjugants (T-89). Laf
+
and Laf
t
were unstable in the plasmid-bearing transconjugant. Plasmid analysis of Laf
−
Laf
s
variants revealed that pPM52 and pPM68 were cured with loss of Laf
+
and Laf
t
. Bacteriocin production and immunity phenotypes were genetically stable in Laf
+
Laf
t
transconjugants not harboring pPM52 and pPM68, suggesting chromosomal integration of the transferred determinants. The data demonstrated intragenic conjugation in
L. acidophilus
and provided direct evidence for involvement of transient plasmid determinants in Laf
+
and Laf
t
.
Images
Publisher
American Society for Microbiology
Subject
Ecology,Applied Microbiology and Biotechnology,Food Science,Biotechnology
Cited by
180 articles.
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