Genetics of lactose utilization in lactic acid bacteria

DEVOS, W; Vaughan, Elaine E.

doi:10.1016/0168-6445(94)90114-7

Cited by 100 publications

(95 citation statements)

References 71 publications

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“…Preliminary studies of CR and its glucose and lactose transport systems have been reported elsewhere (4,10,46), and, recently, two mechanisms controlling the expression of the lactose operon have been suggested: CR mediated by the PTS components and possibly by CcpA and induction by lactose through the antitermination protein LacT (1,15). However, detailed studies of this microorganism have been difficult because of the nearly complete absence of genetic tools.…”

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confidence: 99%

Catabolite repression in Lactobacillus casei ATCC 393 is mediated by CcpA

1997

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The chromosomal ccpA gene from Lactobacillus casei ATCC 393 has been cloned and sequenced. It encodes the CcpA protein, a central catabolite regulator belonging to the LacI-GalR family of bacterial repressors, and shows 54% identity with CcpA proteins from Bacillus subtilis and Bacillus megaterium. The L. casei ccpA gene was able to complement a B. subtilis ccpA mutant. An L. casei ccpA mutant showed increased doubling times and a relief of the catabolite repression of some enzymatic activities, such as N-acetylglucosaminidase and phospho-␤-galactosidase. Detailed analysis of CcpA activity was performed by using the promoter region of the L. casei chromosomal lacTEGF operon which is subject to catabolite repression and contains a catabolite responsive element (cre) consensus sequence. Deletion of this cre site or the presence of the ccpA mutation abolished the catabolite repression of a lacp::gusA fusion. These data support the role of CcpA as a common regulatory element mediating catabolite repression in low-GC-content gram-positive bacteria.

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Catabolite repression in Lactobacillus casei ATCC 393 is mediated by CcpA

1997

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“…Genetic studies of the metabolic pathways for lactose utilization in these gram-positive bacteria have revealed a variety of lac operons that differ from the paradigm known in E. coli (13). The thermophilic yogurt bacteria Streptococcus thermophilus and Lactobacillus bulgaricus contain a highly homologous lacSZ operon in which the ␤-galactosidase (lacZ) gene is located downstream from the lacS gene encoding a lactose permease (LacS), which belongs to the galactoside-pentosehexuronide translocators (27,41,48,49).…”

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Activation of Silent gal Genes in the lac-gal Regulon of Streptococcus thermophilus

Vaughan

Bogaard²,

Catzeddu³

et al. 2001

J Bacteriol

107

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Streptococcus thermophilus strain CNRZ 302 is unable to ferment galactose, neither that generated intracellularly by lactose hydrolysis nor the free sugar. Nevertheless, sequence analysis and complementation studies with Escherichia coli demonstrated that strain CNRZ 302 contained structurally intact genes for the Leloir pathway enzymes. These were organized into an operon in the order galKTE, which was preceded by a divergently transcribed regulator gene, galR, and followed by a galM gene and the lactose operon lacSZ. Results of Northern blot analysis showed that the structural gal genes were transcribed weakly, and only in medium containing lactose, by strain CNRZ 302. However, in a spontaneous galactose-fermenting mutant, designated NZ302G, the galKTE genes were well expressed in cells grown on lactose or galactose. In both CNRZ 302 and the Gal ؉ mutant NZ302G, the transcription of the galR gene was induced by growth on lactose. Disruption of galR indicated that it functioned as a transcriptional activator of both the gal and lac operons while negatively regulating its own expression. Sequence analysis of the gal promoter regions of NZ302G and nine other independently isolated Gal ؉ mutants of CNRZ 302 revealed mutations at three positions in the galK promoter region, which included substitutions at positions ؊9 and ؊15 as well as a single-base-pair insertion at position ؊37 with respect to the main transcription initiation point. Galactokinase activity measurements and analysis of gusA reporter gene fusions in strains containing the mutated promoters suggested that they were gal promoter-up mutations. We propose that poor expression of the gal genes in the galactose-negative S. thermophilus CNRZ 302 is caused by naturally occurring mutations in the galK promoter.After its discovery almost 40 years ago, the Escherichia coli lactose operon, encoding enzymes of lactose metabolism, became the first model for gene regulation (reviewed in reference 4). The key component of this system is the lac repressor (LacI), the product of the lacI gene. The lac operon contains a primary operator (O 1 ), which is the major element of repression by LacI, and two pseudo-operators, which enhance repressor binding to O 1 by cooperativity. Control of the lac operon also involves activation by the cyclic AMP receptor protein.Many other paradigm systems of negative control have since been described, including GalR, one of the two repressors of the gal regulon encoding enzymes of galactose transport and metabolism in E. coli. Regulation of the gal regulon is mediated through GalR, GalS (Gal isorepressor), and the cyclic AMP receptor protein. GalR and GalS negatively regulate transcription of the two promoters of the gal operon, although GalS is not as efficient as GalR (57).The bioconversion of lactose, which is the primary carbon and energy source in milk, into lactic acid is an essential process in industrial dairy fermentations carried out by lactic acid bacteria. Genetic studies of the metabolic pathways for lactose utilization i...

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“…In regard to sugar catabolism, the utilization of lactose is among the most studied in LAB (de Vos & Vaughan, 1994). Lactose permeases have been described in numerous LAB (Barrangou et al, 2003;Leong-Morgenthaler et al, 1991).…”

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confidence: 99%

Identification of lactose phosphotransferase systems in Lactobacillus gasseri ATCC 33323 required for lactose utilization

2012

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Improving the annotation of sugar catabolism-related genes requires functional characterization. Our objective was to identify the genes necessary for lactose utilization by Lactobacillus gasseri ATCC 33323 (NCK334). The mechanism of lactose transport in many lactobacilli is a lactose/ galactose-specific permease, yet no orthologue was found in NCK334. Characterization of an EI knockout strain [EI (enzyme I) is required for phosphotransferase system transporter (PTS) function] demonstrated that L. gasseri requires PTS(s) to utilize lactose. In order to determine which PTS(s) were necessary for lactose utilization, we compared transcript expression profiles in response to lactose for the 15 complete PTSs identified in the NCK334 genome. PTS 6CB (LGAS_343) and PTS 8C (LGAS_497) were induced in the presence of lactose 107-and 53-fold, respectively. However, L. gasseri ATCC 33323 PTS 6CB, PTS 8C had a growth rate similar to that of the wild-type on semisynthetic deMan, Rogosa, Sharpe (MRS) medium with lactose. Expression profiles of L. gasseri ATCC 33323 PTS 6CB, PTS 8C in response to lactose identified PTS 9BC (LGAS_501) as 373-fold induced, whereas PTS 9BC was not induced in NCK334. Elimination of growth on lactose required the inactivation of both PTS 6CB and PTS 9BC. Among the six candidate phospho-b-galactosidase genes present in the NCK334 genome, LGAS_344 was found to be induced 156-fold in the presence of lactose. In conclusion, we have determined that: (1) NCK334 uses a PTS to import lactose; (2) PTS 6CB and PTS 8C gene expression is strongly induced by lactose; and (3) elimination of PTS 6CB and PTS 9BC is required to prevent growth on lactose.

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Genetics of lactose utilization in lactic acid bacteria

Cited by 100 publications

References 71 publications

Catabolite repression in Lactobacillus casei ATCC 393 is mediated by CcpA

Catabolite repression in Lactobacillus casei ATCC 393 is mediated by CcpA

Activation of Silent gal Genes in the lac-gal Regulon of Streptococcus thermophilus

Identification of lactose phosphotransferase systems in Lactobacillus gasseri ATCC 33323 required for lactose utilization

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