Abstract
This study aimed to develop a 16S rRNA PCR-denaturing gradient gel electrophoresis (DGGE) to identify the species level of Lactobacillus casei group and to investigate their characteristics of acid production and inhibitory effect. PCR-DGGE has been developed based on the 16S rRNA gene, and a set of HDA-1-GC and HDA-2, designed at V2-V3 region, and another set of CARP-1-GC and CARP-2, designed at V1 region, have been used. The bacterial strains included L. casei ATCC 393, L. paracasei CCUG 32212, L. rhamnosus ATCC 7469, L. zeae CCUG 35515, and 46 clinical strains of L. casei/paracasei/rhamnosus. Inhibitory effect against Streptococcus mutans and acid production were examined. Results revealed that each type species strain and identified clinical isolate showed its own unique DGGE pattern using CARP1-GC and CARP2 primers. HDA1-GC and HDA2 primers could distinguish the strains of L. paracasei from L. casei. It was found that inhibitory effect of L. paracasei was stronger than L. casei and L. rhamnosus. The acid production of L. paracasei was lower than L. casei and L. rhamnosus. In conclusion, the technique has been proven to be able to differentiate between closely related species in L. casei group and thus provide reliable information of their phenotypic appearances.
Highlights
Lactobacillus strains are extensively used as probiotics in the food industry, and certain Lactobacillus species are of importance in general health, providing a beneficial microflora in the oral cavity [1], intestinal tract [2, 3], and vagina [4]
L. rhamnosus ATCC 7469 and identified clinical isolates revealed a different band from L. zeae CCUG 35515, L. casei ATCC 393, and L. paracasei CCUG 32212
When HDA1 and HDA2 primers were used to produce the denaturing gradient gel electrophoresis (DGGE) patterns of V2-V3 region of 16S rRNA sequences, L. casei ATCC 393 showed the same DGGE pattern as all clinical strains identified as L. casei
Summary
Lactobacillus strains are extensively used as probiotics in the food industry, and certain Lactobacillus species are of importance in general health, providing a beneficial microflora in the oral cavity [1], intestinal tract [2, 3], and vagina [4]. Lactobacillus casei group, especially L. casei, L. paracasei, and L. rhamnosus, has attracted a lot of attention over the last 20 years. This is linked to the considerable economic importance of the L. (para)casei species, which is used in many food and feed applications such as dairy products and has a proven record in human and animal health. The taxonomy among the species in Lactobacillus casei group is still vague.
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