ABSTRACT
In the present work, five hundred and sixty-seven isolates of lactic acid bacteria were recovered from raw bee pollen grains. All isolates were screened for their antagonistic activity against both Gram-positive and Gram-negative pathogenic bacteria. Neutralized supernatants of 54 lactic acid bacteria (LAB) cultures from 216 active isolates inhibited the growth of indicator bacteria. They were phenotypically characterized, based on the fermentation of 39 carbohydrates. Using the simple matching coefficient and unweighted pair group algorithm with arithmetic averages (UPGMA), seven clusters with other two members were defined at the 79% similarity level. The following species were characterized: Lactobacillus plantarum, Lactobacillus fermentum, Lactococcus lactis, Pediococcus acidilactici, Pediococcus pentosaceus, and unidentified lactobacilli. Phenotypic characteristics of major and minor clusters were also identified. Partial sequencing of the 16S rRNA gene of representative isolates from each cluster was performed, and ten strains were assigned to seven species: Lactobacillus plantarum, Lactobacillus fermentum, Lactococcus lactis, Lactobacillus ingluviei, Pediococcus pentosaceus, Lactobacillus acidipiscis and Weissella cibaria. The molecular method used failed to determine the exact taxonomic status of BH0900 and AH3133.
ABSTRACT
A bacteriocin-producing (11,000 AU mL(-1)) strain was isolated from the rhizosphere of healthy Algerian plants Ononis angustissima Lam., and identified as Brevibacillus brevis strain GM100. The bacteriocin, called Bac-GM100, was purified to homogeneity from the culture supernatant, and, based on MALDI-TOF/MS analysis, was a monomer protein with a molecular mass of 4375.66 Da. The 21 N-terminal residues of Bac-GM100 displayed 65% homology with thurincin H from Bacillus thuringiensis. Bac-GM100 was extremely heat-stable (20 min at 120 °C), and was stable within a pH range of 3-10. It proved sensitive to various proteases, which demonstrated its protein nature. It was also found to display a bactericidal mode of action against gram-negative (Salmonella enteric ATCC 43972, Pseudomonas aeruginosa ATCC 49189, and Agrobacterium tumefaciens C58) and gram-positive (Enterococcus faecalis ENSAIA 631 and Staphylococcus aureus ATCC 6538) bacteria, and a fungistatic mode of action against the pathogenic fungus Candida tropicalis R2 CIP 203.
