Molecular typing of Lactobacillus delbrueckii of dairy origin by PCR-RFLP of protein-coding genes.
Thirty-five strains of Lactobacillus delbrueckii subsp. lactis and subsp. bulgaricus isolated from dairy products were typed by restriction fragment length polymorphism (RFLP) of protein-coding genes. The strains were analysed by RFLP of PCR amplified, infragenic fragments of the following housekeeping genes: beta-galactosidase, lactose permease, and proline dipeptidase. Sequencing of the variable regions of the 16S rDNA was then performed on a reduced number of strains. PCR-RFLP analysis evidenced wide strain heterogeneity. Strains were grouped into genotypes according to both subspecies assignment and infra-species genetic polymorphism. This polymorphism was related to the presence of microbial groups within subspecies populations. The low infra-species sequence polymorphism detected in the variable region of the 16S rRNA gene did not enable to group the strains with the same sensitivity reached by PCR-RFLP of protein-coding genes. PCR-RFLP of protein-coding genes applied to L. delbrueckii seems a promising tool to evaluate microbial diversity within bacterial subpopulations. Differences among bacterial subpopulations based upon molecular heterogeneity in protein-coding genes would enable to better understand the role of strains from different ecological niches.
Giraffa
G
G
Department of Microbiology and Enzymology, Istituto Sperimentale Lattiero Caseario, Via A. Lombardo 11, 26900 Lodi, Italy. ggiraffa@ilclodi.it
Lazzi
C
C
Gatti
M
M
Rossetti
L
L
Mora
D
D
Neviani
E
E
D015373:Bacterial Typing Techniques; D016000:Cluster Analysis; D004269:DNA, Bacterial / Q000737:chemistry / Q000302:isolation & purification*; D004275:DNA, Ribosomal / Q000737:chemistry; D003611:Dairy Products / Q000382:microbiology*; D004150:Dipeptidases / Q000235:genetics; D029968:Escherichia coli Proteins; D005516:Food Microbiology; D005838:Genotype; D007778:Lactobacillus / Q000145:classification* / Q000201:enzymology / Q000235:genetics; D026901:Membrane Transport Proteins / Q000235:genetics; D009004:Monosaccharide Transport Proteins; D010802:Phylogeny; D016133:Polymerase Chain Reaction; D012150:Polymorphism, Restriction Fragment Length; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D015183:Restriction Mapping; D027981:Symporters; D001616:beta-Galactosidase / Q000235:genetics
D004269:DNA, Bacterial; D004275:DNA, Ribosomal; D029968:Escherichia coli Proteins; C050221:LacY protein, E coli; D026901:Membrane Transport Proteins; D009004:Monosaccharide Transport Proteins; D012336:RNA, Ribosomal, 16S; D027981:Symporters; C021499:lactose permease; D001616:beta-Galactosidase; D004150:Dipeptidases; C022449:proline dipeptidase