Identify specific probiotic strains.

Dietary supplement sales have significantly grown in the past few years, suggesting consumers are seeking dietary sources as a way to keep themselves healthy. Probiotics continue to grow in popularity as both a supplement and an ingredient in dairy foods.

Due to the large number of probiotic strains, and because many closely resemble each other, proper strain identification is one of the greatest challenges in probiotic research. Identification is necessary for determining safety, making the proper representation of strains on product labels and predicting functionality. Several efforts at California Polytechnic State University (Dairy Products Technology Center, San Luis Obispo, CA 93407) are addressing this challenge.

In collaboration with colleagues at North Carolina State University (Raleigh, NC), California Polytechnic scientists have embarked on a large-scale effort to sequence the Lactobacillus acidophilus genome. As the DNA sequences are completed, they are compared with published sequences from other, more completely studied bacteria to help determine their function. The complete genomic sequence could help identify genes important to the functionality of probiotic bacteria and provide a way to improve the expression, regulation and attributes of important characteristics.

Others at California Polytechnic have attempted to classify and identify a collection of probiotic lactobacilli and Bifidobacteria using such phenotypic and gene-based methods as carbohydrate fermentation patterns, fatty acid analysis, pulsed-field gel electrophoresis and 16S rDNA sequencing. These methods have provided researchers with insight into the phylogenetic distance between different probiotic strains.

Also, researchers are applying terminal restriction fragment pattern analysis, a DNA-based rapid identification technique, to quantitatively describe changes in microbial populations in human fecal samples obtained from those who have eaten probiotic-containing yogurt. It is believed that a prime mechanism of probiotic bacterial function is probiotics' influence on the population structure of the human fecal microbial community. Results will assist researchers in providing scientific support for understanding the clinical effects of eating probiotic-containing dairy foods.

Further information. On sequencing: Raul Cano; on classification and identification: Mary Ellen Sanders; on microbial populations: Christopher Kitts; phone: [phone]; fax: [phone].