Bacteriocins of staphylococci and oral streptococci

Contains fulltext : mmubn000001_250491249.pdf (publisher's version ) (Open Access)Promotor : G. Vogels164 p

Identification of mesophilic lactic acid bacteria by using polymerase chain reaction-aplified variable regions of 16S rRNA and specific DNA probes.

Specific DNA probes based on variable regions V1 and V3 of 16S rRNA of lactic acid bacteria were designed. These probes were used in hybridization experiments with variable regions amplified by using the polymerase chain reaction. In this way, a rapid and sensitive method was developed for the identification and classification of Lactococcus and Leuconostoc species

Genetic marking of Lactococcus lactis shows its survival in the human gastro-intestinal tract.

A human feeding study was performed with Lactococcus lactis TC165.5, which is genetically marked by insertion of the sucrose-nisin conjugative transposon Tn5276 and chromosomal resistance to rifampin and streptomycin. The fate of strain TC165.5 and its nucleic acids was monitored by conventional plating methods and by molecular detection techniques based on specific PCR amplification of the nisin (nisA) gene from DNA extracted from human feces. A method was developed for the efficient extraction of microbial DNA from human feces. The results show that a fraction of viable cells of L. lactis TC165.5 survived passage through the human gastrointestinal tract. Only cells that passed within 3 days of ingestion could be recovered from the feces of the volunteers, and they accounted for approximately 1% of the total number of cells consumed. The presence of nisA in DNA extracted from feces could be detected up to 4 days, when viable cells were no longer present

Detection and characterization of lactose-utilizing Lactococcus spp. in environmental ecosystems.

The presence of lactose-utilizing Lactococcus species in nondairy environments was studied by using identification methods based on PCR amplification and (sub)species-specific probes derived from 16S rRNA sequences. Environmental isolates from samples taken on cattle farms and in the waste flow of a cheese production plant were first identified to the genus level, using a Lactococcus genus-specific probe. Isolates which showed a positive signal with this probe were further identified to the (sub)species level. Lactococcus lactis isolates were also characterized at the phenotypic level for the ability to hydrolyze arginine, to ferment citrate, and to produce proteases and bacteriocins. With specific PCR amplifications, the presence of sequences related to citP, coding for citrate permease; prtP, coding for protease; and nisA or nisZ, the structural genes for production of nisin A or nisin Z, respectively, was verified. By these methods, it was possible to isolate lactococci from various environmental sources, such as soil, effluent water, and the skin of cattle. The strains of L. lactis isolated differed in a number of properties, such as the ability to hydrolyze arginine or the absence of citP-related sequences, from those found in industrial starter cultures. The results indicate that the majority of the industrially produced lactococci do not survive outside the dairy environment, although natural niches are available. However, from those niches strains with the potential to be developed into novel starter cultures may be isolated