Exopolysaccharide-producing strains of thermophilic lactic acid bacteria cluster into groups according to their EPS structure

Marshall, Valerie M.; Laws, Andrew P.; Gu, Yu‐Cheng; Levander, Fredrik; Rådström, Peter; Vuyst, Luc De; Degeest, Bart; Vaningelgem, Frederik; Dunn, H. J.; Elvin, Mark

doi:10.1046/j.1472-765x.2001.00937.x

Cited by 51 publications

(26 citation statements)

References 22 publications

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“…The EPS composition among B. longum subsp. longum strains seems diverse, which agrees with the strain variation found within other genera such as Streptococcus, Lactococcus and Lactobacillus (Broadbent et al, 2003;Marshall et al, 2001). Although strain CRC 002 might produce multiple EPS polymers, the extraction procedure recovers all EPS present in the culture supernatant, and the compositional analysis did not show the presence of rhamnose.…”

Section: Discussionsupporting

confidence: 79%

Sugar source modulates exopolysaccharide biosynthesis in Bifidobacterium longum subsp. longum CRC 002

et al. 2010

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The effect of four sugars (glucose, galactose, lactose and fructose) on exopolysaccharide (EPS) production by Bifidobacterium longum subsp. longum CRC 002 was evaluated. More EPS was produced when CRC 002 was grown on lactose in the absence of pH control, with a production of 1080±120 mg EPS l "1 (P,0.01) after 24 h of incubation. For fructose, galactose and glucose, EPS production was similar, at 512±63, 564±165 and 616±93 mg EPS l "1 , respectively. The proposed repeating unit composition of the EPS is 2 galactose to 3 glucose. The effect of sugar and fermentation time on expression of genes involved in sugar nucleotide production (galK, galE1, galE2, galT1, galT2, galU, rmlA, rmlB1 and rmlCD) and the priming glycosyltransferase (wblE) was quantified using real-time reverse transcription PCR. A significantly higher transcription level of wblE (9.29-fold) and the genes involved in the Leloir pathway (galK, 4.10-fold; galT1, 2.78-fold; and galE2, 4.95-fold) during exponential growth was associated with enhanced EPS production on lactose compared to glucose. However, galU expression, linking glucose metabolism with the Leloir pathway, was not correlated with EPS production on different sugars. Genes coding for dTDP-rhamnose biosynthesis were also differentially expressed depending on sugar source and growth phase, although rhamnose was not present in the composition of the EPS. This precursor may be used in cell wall polysaccharide biosynthesis. These results contribute to understanding the changes in gene expression when different sugar substrates are catabolized by B. longum subsp. longum CRC 002.

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Section: Discussionsupporting

confidence: 79%

Sugar source modulates exopolysaccharide biosynthesis in Bifidobacterium longum subsp. longum CRC 002

et al. 2010

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“…Compositional and structural analyses have revealed that the EPS produced by RD534 is composed primarily of D-glucose and D-galactose in a molar ratio of 1:1 (data not shown). The EPS of RD534 is thus similar to those produced by other S. thermophilus strains (38,44). S. thermophilus RD534 is sensitive to a group of closely related virulent S. thermophilus phages ( Fig.…”

Section: Phages Infecting S Thermophilus Rd534 S Thermophilussupporting

confidence: 61%

Genomic Organization and Molecular Analysis of Virulent Bacteriophage 2972 Infecting an Exopolysaccharide-Producing Streptococcus thermophilus Strain

Lévesque

Duplessis

Labonté

et al. 2005

Appl Environ Microbiol

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The Streptococcus thermophilus virulent pac-type phage 2972 was isolated from a yogurt made in France in 1999. It is a representative of several phages that have emerged with the industrial use of the exopolysaccharide-producing S. thermophilus strain RD534. The genome of phage 2972 has 34,704 bp with an overall G؉C content of 40.15%, making it the shortest S. thermophilus phage genome analyzed so far. Forty-four open reading frames (ORFs) encoding putative proteins of 40 or more amino acids were identified, and bioinformatic analyses led to the assignment of putative functions to 23 ORFs. Comparative genomic analysis of phage 2972 with the six other sequenced S. thermophilus phage genomes confirmed that the replication module is conserved and that cos-and pac-type phages have distinct structural and packaging genes. Two group I introns were identified in the genome of 2972. They interrupted the genes coding for the putative endolysin and the terminase large subunit. Phage mRNA splicing was demonstrated for both introns, and the secondary structures were predicted. Eight structural proteins were also identified by N-terminal sequencing and/or matrixassisted laser desorption ionization-time-of-flight mass spectrometry. Detailed analysis of the putative minor tail proteins ORF19 and ORF21 as well as the putative receptor-binding protein ORF20 showed the following interesting features: (i) ORF19 is a hybrid protein, because it displays significant identity with both pac-and cos-type phages; (ii) ORF20 is unique; and (iii) a protein similar to ORF21 of 2972 was also found in the structure of the cos-type phage DT1, indicating that this structural protein is present in both S. thermophilus phage groups. The implications of these findings for phage classification are discussed.

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“…Our results suggest that there was an increase in the levels of UDPglc and UDPgal when galU was overexpressed and that the Glc1P/UDPglc ratios were lower (Tables 4 and 5). The EPS from LY03 has recently been shown to contain glucose, galactose, and N-acetylgalactosamine (22), and UDP-N-acetylgalactosamine could thus be a limiting precursor in addition to UDPglc and UDPgal. However, another recent study indicated that production of this precursor is not a limiting factor for EPS production in LY03 (11).…”

Section: Discussionmentioning

confidence: 99%

Enhanced Exopolysaccharide Production by Metabolic Engineering of Streptococcus thermophilus

Levander

Svensson

Rådström

2002

Appl Environ Microbiol

126

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It is possible that the low levels of production of exopolysaccharides (EPSs) by lactic acid bacteria could be improved by altering the levels of enzymes in the central metabolism that influence the production of precursor nucleotide sugars. To test this hypothesis, we identified and cloned the galU gene, which codes for UDP glucose pyrophosphorylase (GalU) in Streptococcus thermophilus LY03. Homologous overexpression of the gene led to a 10-fold increase in GalU activity but did not have any effect on the EPS yield when lactose was the carbon source. However, when galU was overexpressed in combination with pgmA, which encodes phosphoglucomutase (PGM), the EPS yield increased from 0.17 to 0.31 g/mol of carbon from lactose. A galactose-fermenting LY03 mutant (Gal ؉ ) with increased activities of the Leloir enzymes was also found to have a higher EPS yield (0.24 g/mol of carbon) than the parent strain. The EPS yield was further improved to 0.27 g/mol of carbon by overexpressing galU in this strain. However, the highest EPS yield, 0.36 g/mol of carbon, was obtained when pgmA was knocked out in the Gal ؉ strain. Measurements of the levels of intracellular metabolites in the cultures revealed that the Gal ؉ strains had considerably higher glucose 1-phosphate levels than the other strains, and the strain lacking PGM activity had threefold-higher levels of glucose 1-phosphate than the other Gal ؉ strains. These results show that it is possible to increase EPS production by altering the levels of enzymes in the central carbohydrate metabolism.Exopolysaccharides (EPSs) produced by lactic acid bacteria are important for the texture of many fermented milk products. There is great diversity in the composition and structure of these EPSs, which results in different properties (for a review, see reference 12). A variety of EPSs with different repeating units and chain lengths have been found in Streptococcus thermophilus, and diversity is also found in the increasing number of eps operons that are being sequenced (1, 7, 32). The operons consist of a more conserved region with genes that are thought to be involved in regulation, chain length determination, and export, which is followed by a variable region with genes coding for glycosyltransferases and enzymes involved in polymerization and export of the EPSs. The information being accumulated could form the basis for the construction of new tailor-made polysaccharides by genetic engineering (35). However, before the variety of EPSs from lactic acid bacteria can be fully exploited, ways of enhancing the low levels of production must be found. For example, the amount of EPS produced by S. thermophilus normally is less than 1% of the amount of the carbohydrate source (12). EPSs are synthesized from activated nucleotide sugars, and a potential bottleneck in EPS production could be the low levels of these precursors. In S. thermophilus, which possesses the Leloir pathway, UDP glucose (UDPglc) and UDP galactose (UDPgal) can be formed from either the glucose or the galactose moiety ...

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Exopolysaccharide-producing strains of thermophilic lactic acid bacteria cluster into groups according to their EPS structure

Cited by 51 publications

References 22 publications

Sugar source modulates exopolysaccharide biosynthesis in Bifidobacterium longum subsp. longum CRC 002

Sugar source modulates exopolysaccharide biosynthesis in Bifidobacterium longum subsp. longum CRC 002

Genomic Organization and Molecular Analysis of Virulent Bacteriophage 2972 Infecting an Exopolysaccharide-Producing Streptococcus thermophilus Strain

Enhanced Exopolysaccharide Production by Metabolic Engineering of Streptococcus thermophilus

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