(GTG)(5)-PCR fingerprinting of lactobacilli isolated from cervix of healthy women

Identification, Classification and Screening for γ-Amino-butyric Acid Production in Lactic Acid Bacteria from Cambodian Fermented Foods

Screening for various types of lactic acid bacteria (LAB) that form the biological agent γ-amino-butyric acid (GABA) is important to produce different kinds of GABA-containing fermented foods. So far, no GABA-producing LAB have been reported from Cambodian fermented foods. Most small-scale fermentations and even some industrial processes in this country still rely on indigenous LAB. The application of GABA-producing autochthonous starters would allow the production of Cambodian fermented foods with an additional nutritional value that meet the population's dietary habits and that are also more attractive for the international food market. Matrix-assisted laser desorption/ionizing time-of-flight mass spectrometry (MALDI-TOF MS) and partial 16S rDNA sequencing were used to identify 68 LAB isolates from Cambodian fermented foods. These isolates were classified and grouped with (GTG)5 rep-PCR, resulting in 50 strains. Subsequently, all strains were investigated for their ability to produce GABA by thin layer chromatography. GABA-positive strains were further analyzed by the GABase assay. Of the six GABA-positive LAB strains-one Lactobacillus futsaii, two Lactobacillus namurensis, and three Lactobacillus plantarum strains-two Lactobacillus plantarum strains produced high amounts of GABA (20.34 mM, 16.47 mM). These strains should be further investigated for their potential application as GABA-producing starter cultures in the food applications.

Comparative Genomics Reveals Biomarkers to Identify Lactobacillus Species

Bacteria possessing multiple copies of 16S rRNA (rrs) gene demonstrate high intragenomic heterogeneity. It hinders clear distinction at species level and even leads to overestimation of the bacterial diversity. Fifty completely sequenced genomes belonging to 19 species of Lactobacillus species were found to possess 4-9 copies of rrs each. Multiple sequence alignment of 268 rrs genes from all the 19 species could be classified into 20 groups. Lactobacillus sanfranciscensis TMW 1.1304 was the only species where all the 7 copies of rrs were exactly similar and thus formed a distinct group. In order to circumvent the problem of high heterogeneity arising due to multiple copies of rrs, 19 additional genes (732-3645 nucleotides in size) common to Lactobacillus genomes, were selected and digested with 10 Type II restriction endonucleases (RE), under in silico conditions. The following unique gene-RE combinations: recA (1098 nts)-HpyCH4 V, CviAII, BfuCI and RsaI were found to be useful in identifying 29 strains representing 17 species. Digestion patterns of genes-ruvB (1020 nts), dnaA (1368 nts), purA (1290 nts), dnaJ (1140 nts), and gyrB (1944 nts) in combination with REs-AluI, BfuCI, CviAI, Taq1, and Tru9I allowed clear identification of an additional 14 strains belonging to 8 species. Digestion pattern of genes recA, ruvB, dnaA, purA, dnaJ and gyrB can be used as biomarkers for identifying different species of Lactobacillus.

Selection of enhanced antimicrobial activity posing lactic acid bacteria characterised by (GTG)5-PCR fingerprinting

The aim of the study was a detail evaluation of genetic diversity among the lactic acid bacteria (LAB) strains having an advantage of a starter culture in order to select genotypically diverse strains with enhanced antimicrobial effect on some harmfull and pathogenic microorganisms. Antimicrobial activity of LAB was performed by the agar well diffusion method and was examined against the reference strains and foodborne isolates of Bacillus cereus, Listeria monocytogenes, Escherichia coli, Staphylococcus aureus and Salmonella Typhimurium. Antifungal activity was tested against the foodborne isolates of Candida parapsilosis, Debaromyces hansenii, Kluyveromyces marxianus, Pichia guilliermondii, Yarowia lipolytica, Aspergillus brasiliensis, Aspergillus versicolor, Cladosporium herbarum, Penicillium chrysogenum and Scopulariopsis brevicaulis. A total 40 LAB strains representing Lactobacillus (23 strains), Lactococcus (13 strains) and Streptococcus spp. (4 strains) were characterised by repetitive sequence based polymerase chain reaction fingerprinting which generated highly discriminatory profiles, confirmed the identity and revealed high genotypic heterogeneity among the strains. Many of tested LAB demonstrated strong antimicrobial activity specialised against one or few indicator strains. Twelve LAB strains were superior in suppressing growth of the whole complex of pathogenic bacteria and fungi. These results demonstrated that separate taxonomic units offered different possibilities of selection for novel LAB strains could be used as starter cultures enhancing food preservation.

Probiotic attributes of Lactobacillus fermentum isolated from human feces and dairy products

The objective of this study was to characterize native Lactobacillus fermentum isolates for their probiotic attributes. Accordingly, 12 L. fermentum isolates selected from indigenous fermented dairy products and infant fecal samples were evaluated for their probiotic properties by in vitro and PCR methods. The cultures exhibited high tolerance to acid and bile as well as survival in simulated transit fluids (above 70 %). Cell surface hydrophobicity was in the range of 0.55-57.69 % for xylene and 0.45-77.12 % for hexadecane, whereas auto-aggregation ranged between 9 and 62 %. Isolates exhibited efficient binding to mucin and fibronectin, bile salt hydrolase activity, cholesterol assimilation (49-76 %), and radical scavenging activity (37-77 %). The isolates demonstrated antibacterial activity against Listeria monocytogenes Scott A and Micrococcus luteus ATCC 9341. Molecular fingerprinting and identification of the isolates were achieved by PCR with GTG5 as well as 16S rRNA, phenylalanyl-tRNA synthetase alpha subunit (pheS), and RNA polymerase alpha subunit (rpoA) genes. This revealed the genomic diversity of the isolates from the two sources. Gene-specific amplification of probiotic marker genes was attained by PCR-based methods, and resultant products were sequenced. Multiple sequence alignment of the probiotic marker genes using bioinformatics revealed similarity to completely sequenced genomes of L. fermentum CECT 5716 and IFO 3956 with a few variations in mucin-binding protein gene sequences. Isolates designated as L. fermentum MCC 2759 and L. fermentum MCC 2760 showed the best probiotic attributes with high survival in simulated gastrointestinal fluids, in vitro adhesion, cholesterol reduction, and high antioxidative potential. Thus, these cultures could be potential probiotic candidates for application as functional foods.

Lactobacillus faecis sp. nov., isolated from animal faeces

Three lactic acid bacteria were isolated from faeces of a jackal (Canis mesomelas) and raccoons (Procyron lotor). The isolates formed a subcluster in the Lactobacillus salivarius phylogenetic group, closely related to Lactobacillus animalis , Lactobacillus apodemi and Lactobacillus murinus , by phylogenetic analysis based on 16S rRNA and recA gene sequences. Levels of DNA–DNA relatedness revealed that the isolates belonged to the same taxon and were genetically separated from their phylogenetic relatives. The three strains were non-motile, obligately homofermentative and produced l-lactic acid as the main end-product from d-glucose. The strains metabolized raffinose. The major cellular fatty acids in the three strains were C16 : 0, C18 : 1ω9c and C19 : 1 cyclo 9,10. Based on the data provided, it is concluded that the three strains represent a novel species of the genus Lactobacillus , for which the name Lactobacillus faecis sp. nov. is proposed. The type strain is AFL13-2T ( = JCM 17300T = DSM 23956T).