The aims of this study were to investigate the diversity of lactic acid bacteria (LAB) isolated from traditional Mongolian dairy products, and to estimate the probiotic potential of the isolated strains. We collected 66 samples of the traditional Mongolian dairy products tarag (n = 45), airag (n = 7), aaruul (n = 8), byasulag (n = 1) and eezgii (n = 5), from which 543 LAB strains were isolated and identified based on 16S ribosomal DNA sequence. The predominant species of those products were Lactobacillus (L.) delbrueckii ssp. bulgaricus, L. helveticus, L. fermentum, L. delbrueckii ssp. lactis and Lactococcus lactis ssp. lactis. However, we could not detect any LAB strains from eezgii. All LAB isolates were screened for tolerance to low pH and to bile acid, gas production from glucose, and adherence to Caco-2 cells. In vitro, we found 10 strains possess probiotic properties, and almost identified them as L. plantarum or L. paracasei subspecies, based on 16S ribosomal DNA and carbohydrate fermentation pattern. These strains were differentiated from each other individually by randomly amplified polymorphic DNA analysis. Additionally, it was notable that 6/10 strains were isolated from camel milk tarag from the Dornogovi province.

The biosynthetic pathways for putrescine (Put) in Vibrio p arahaemolyticus were delineated by measuring activities of the enzymes which would be involved in its biosynthesis. Experiments with labeled arginine and ornithine revealed that both of these amino acids were converted into Put by intact cells. The activities of three enzymes, arginine decarboxylase (ADC), ornithine decarboxylase (ODC), and agmatine ureohydrolase (AUH), were detected in cell extracts. ADC and ODC of V. parahaemolyticus were similar in the following properties to the corresponding enzymes of Escherichia coli: 1) both decarboxylases showed a pH optimum at 8.25 and required pyridoxal phosphate and dithiothreitol for full activity; 2) while ODC was considerably activated by GTP, ADC was only slightly; 3) both decarboxylases were inhibited by polyamines ; 4) ADC was inhibited by difluoromethylarginine, a potent inhibitor of bacterial ADC. However, in contrast to the corresponding enzymes of E. coli, the V. parahaemolyticus ADC showed no requirement for Mg2+, and the AUH was active over a wide pH range of 8.5-9.5 with a maximum at pH 9.0. Furthermore, in all 6 strains tested, the activity of ADC was obviously high compared with that of ODC, and AUH was present with a relatively high activity. Cultivation of these strains at a suboptimal NaCl concentration (0.5%) resulted in a pronounced increase in both ADC and AUH activities. These observations suggest that the important pathway for Put biosynthesis in V. parahaemolyticus is the decarboxylation of arginine by ADC and the subsequent hydrolysis of its product, agmatine, by AUH.

Nongrowing Vibrio parahaemolyticus cells rapidly produced putrescine (Put) from added arginine when subjected to a low osmotic stress. This phenomenon was characterized in connection with a regulatory mechanism of the responsible enzymes, arginine decarboxylase (ADC) and agmatine ureohydrolase (AUH). NaCl, KC1, LiC1, sucrose, and glycerol were used as solutes to prepare the resuspending media with various osmolalities. Regardless of whether the solutes were electrolytes or non-