Comparative analysis of the exopolysaccharide biosynthesis gene clusters from four strains of Lactobacillus rhamnosus

Abstract

The exopolysaccharide (EPS) biosynthesis gene clusters of four Lactobacillus rhamnosus strains consist of chromosomal DNA regions of 18·5 kb encoding 17 ORFs that are highly similar among the strains. However, under identical conditions, EPS production varies considerably among these strains, from 61 to 1611 mg l−1. Fifteen genes are co-transcribed starting from the first promoter upstream of wzd. Nevertheless, five transcription start sites were identified by 5′-RACE PCR analysis, and these were associated with promoter sequences upstream of wzd, rmlA, welE, wzr and wzb. Six potential glycosyltransferase genes were identified that account for the assembly of the heptasaccharide repeat unit containing an unusually high proportion of rhamnose. Four genes involved in the biosynthesis of the sugar nucleotide precursor dTDP-l-rhamnose were identified in the EPS biosynthesis locus, which is unusual for lactic acid bacteria. These four genes are expressed from their own promoter (P2), as well as co-transcribed with the upstream EPS genes, resulting in coordinated production of the rhamnose precursor with the enzymes involved in EPS biosynthesis. This is believed to be the first report demonstrating that the sequence, original organization and transcription of genes encoding EPS production are highly similar among four strains of Lb. rhamnosus, and do not vary with the amount of EPS produced.

Biosynthesis, Purification and Biotechnological Use of Exopolysaccharides Produced by Lactic Acid Bacteria

“…Thus, in Lb. rhamnosus, they are associated to the EPS operon and they can be transcribed either from their own promoter or together with the EPS operon genes (Péant et al, 2005). There is a great variability in the genes involved in the synthesis of the repeating units.…”

EPS producing microorganisms from municipal wastewater activated sludge

“…Moreover, few studies investigated the variation of microbial community in WWTP with respect to seasonal changes due to the variation of environmental factors particularly the temperature and the composition of wastewater. There were few researches [7] comparing the EPS production among the strains based on their genetics. This study presented three parts.…”

Characterization of surface molecules from bacterial cells involved in the potential probiotic activity of natural lactobacilli isolates

“…rhamnosus ATCC9595 do čak 2350 mg/l u soju Lb. rhamnosus RW-9595M što je ujedno i do sada najviša opisana produkcija HeEPS-a kod BMK (Péant et al, 2005).…”

“…plantarum EP56, koji je ujedno i prvi predstavnik svoje vrste za koji je izolovan i biohemijski okarakterisan EPS (Tallon et al, 2003), produkuje dva EPS-a jedan koji se oslobađa u medijum i koji je manje molekulske mase ( što je slučaj sa proteinom koji ima istu funkciju kod Lb. rhamnosus RW-9595M (Péant et al, 2005). ORF 8 je homolog sa 1,6-galaktoziltransferazom, što bi značilo da može da ima ulogu u dodavanju galaktoze pri formiranju EPS ponavljajućih jedinica EPS-CG11.…”

“…ORF 6 i 7 su polisaharid-polimeraze i njihova homologija na aminokiselinskom nivou je slična homologiji koju su pokazali wzx i wzy ORF soja Lb. rhamnosus RW-9595M sa okarakterisanim proteinima St. thermophilus (Péant et al, 2005). Flipaza (Wzx) kao integralni membranski protein, bi trebalo da vrši translokaciju EPS subjednica kroz citoplazmatičnu membranu, dok polisaharid polimeraza Wzy povezuje ponavljajuće jedinice EPS-a i tako formira dugački lanac EPS-a .…”