Genetic diversity in Swiss cheese starter cultures assessed by pulsed field gel electrophoresis and arbitrarily primed PCR.
OBJECTIVE
To assess intraspecific genetic heterogeneity among commercial Swiss cheese starter culture strains of Lactobacillus helveticus, Streptococcus thermophilus and Propionibacterium freudenreichii and to compare the efficacy of two genetic typing methods.


RESULTS
Two genetic typing methods, pulsed field gel electrophoresis (PFGE) and arbitrarily primed PCR (AP-PCR), were used. Nine Strep. thermophilus strains revealed eight PFGE and five AP-PCR genotypes. Seventeen Lactobacillus strains yielded 16 and five genotypes by PFGE and AP-PCR, respectively. Eleven Propionibacterium strains yielded 10 PFGE genotypes. Cluster analysis of PFGE profiles generated similarity coefficients for Strep. thermophilus, Lact. helveticus and Prop. freudenreichii strains of 29.5%, 60.3%, and 30.5%, respectively. Milk acidification rates for Strep. thermophilus and Lact. helveticus were determined.


CONCLUSIONS
Pulsed field gel electrophoresis is more discriminatory than AP-PCR. The Lact. helveticus group is more homogeneous than the other species examined. Strains with > 87% similarity by PFGE consistently had the same acidification rate and AP-PCR profile.


CONCLUSIONS
Bacterial strains sold for Swiss cheese manufacture in the United States are genetically diverse. Clustering of genetically related bacteria may be useful in identifying new strains with industrially relevant traits.
Jenkins
J K
JK
Department of Food Science and Technology, The Ohio State University, Columbus, OH 43210, USA.
Harper
W J
WJ
Courtney
P D
PD
D015373:Bacterial Typing Techniques; D002478:Cells, Cultured; D002611:Cheese / Q000382:microbiology*; D003470:Culture Media; D016521:Electrophoresis, Gel, Pulsed-Field / Q000379:methods*; D007778:Lactobacillus / Q000145:classification / Q000235:genetics* / Q000254:growth & development / Q000302:isolation & purification; D010802:Phylogeny; D016133:Polymerase Chain Reaction / Q000379:methods*; D011424:Propionibacterium / Q000145:classification / Q000235:genetics* / Q000254:growth & development / Q000302:isolation & purification; D013291:Streptococcus / Q000145:classification / Q000235:genetics* / Q000254:growth & development / Q000302:isolation & purification
D003470:Culture Media