Inducible gene expression and environmentally regulated genes in lactic acid bacteria

Kok, Jan

doi:10.1007/bf00395930

Cited by 31 publications

(11 citation statements)

References 71 publications

(55 reference statements)

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“…It would be interesting to elucidate whether such general stress proteins and their regulator σ B are present in L. lactis . The striking properties of recA in relation to heat shock response and oxidative stress suggest that control of stress responses in L. lactis is markedly different from other bacteria, as has been noted for the control of other cellular functions [89].…”

Section: Stressmentioning

confidence: 92%

Environmental stress responses inLactococcus lactis

1999

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Bacteria can encounter a variety of physical conditions during their life. Bacterial cells are able to survive these (often adverse) conditions by the induction of specific or general protection mechanisms. The lactic acid bacterium Lactococcus lactis is widely used for the production of cheese. Before and during this process as well as in its natural habitats, it is subjected to several stressful conditions. Such conditions include oxidation, heating and cooling, acid, high osmolarity/dehydration and starvation. In many environments combinations of these parameters occur. Understanding the stress response behaviour of L. lactis is important to optimize its application in industrial fermentations and is of fundamental interest as L. lactis is a non‐differentiating Gram‐positive bacterium. The stress response mechanisms of L. lactis have drawn increasing attention in recent years. The presence in L. lactis of a number of the conserved systems (e.g. the heat shock proteins) has been confirmed. Some of the regulatory mechanisms responding to an environmental stress condition are related to those found in other Gram‐positive bacteria. Other stress response systems are conserved at the protein level but are under control of mechanisms unique for L. lactis. In a number of cases exposure to a single type of stress provides resistance to other adverse conditions. The unravelling of the underlying regulatory systems gives insight into the development of such cross resistance. Taken together, L. lactis has a unique set of stress response mechanisms, most of which have been identified on the basis of homology with proteins known from other bacteria. A number of the regulatory elements may provide attractive tools for the development of food grade inducible gene expression systems. Here an overview of the growth limits of L. lactis and the molecular characterization of its stress resistance mechanisms is presented.

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Section: Stressmentioning

confidence: 92%

Environmental stress responses inLactococcus lactis

1999

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“…Among the large number of promoters identified in L. lactis (de Vos and Simons, 1994; Kok, 1996), a majority contains the consensus −35 (TTGACA) and the consensus −10 (TATAAT) sequence, resembling the vegetative promoters of E. coli (Harley and Reynolds, 1987) and Bacillus subtilis (Moran et al ., 1982). In addition, approximately half of the L. lactis promoters contain an extended −10 motif, comprising a TGN sequence located immediately upstream of the −10 region (de Vos and Simons, 1994; Bidnenko et al ., 1995).…”

Section: Introductionmentioning

confidence: 99%

Molecular characterization of the pH‐inducible and growth phase‐dependent promoter P170 of Lactococcus lactis

Madsen¹,

Arnau²,

Vrang³

et al. 1999

Molecular Microbiology

107

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SummaryIn a previous study, we described the use of transposon Tn917-LTV1 for identi®cation of environmentally regulated promoters in Lactococcus lactis. Here, we report the molecular analysis of one of these promoters, P170, that is upregulated at low pH during the transition to stationary phase. The minimal DNA region required for both promoter activity and pH regulation was mapped to a 51 bp fragment located 7 bp upstream of the transcriptional start site. This fragment lacked the consensus À35 promoter region, but it contained an`extended' À10 promoter region. When a 28 bp segment, containing the consensus À35 region and 22 bp upstream of this in a constitutive promoter, was replaced with the corresponding sequence of P170, the hybrid promoter became regulated by pH and growth phase. This demonstrates that the P170 segment contains a cis-acting sequence involved in the control of promoter regulation. Transcriptional analysis showed that P170 is responsible for the transcription of a monocistronic gene orfX encoding a polypeptide homologous to a hypothetical protein from Bacillus subtilis. Analysis of total RNA from L. lactis grown at constant pH con®rmed that transcription from P170 was induced between pH 6.5 and pH 6.0, but only when the culture entered stationary phase. Deletion analysis and chemical mutagenesis of P170 de®ned a speci®c region within the untranslated mRNA leader that is able to modulate the expression level directed by the P170 promoter. Deletion of a 72 bp HaeIII fragment from this leader region resulted in a 150-to 200-fold increase in the level of gene expression, without affecting the regulation. The functionality was con®rmed by introducing this modulating element downstream of other lactococcal promoters.

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“…In E. coli, such sites are most frequently found between positions Ϫ50 and ϩ30 of the respective promoters (4). In L. lactis, few combinations of regulatory proteins and their operator are known (24); however, the E. coli paradigm may apply.…”

Section: Discussionmentioning

confidence: 99%

Regulation of Expression of the Lactococcus lactis Histidine Operon

1999

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In Lactococcus lactis, the his operon contains all the genes necessary for histidine biosynthesis. It is transcribed from a unique promoter, localized 300 bp upstream of the first gene. The region corresponding to the untranslated 5′ end of the transcript, named the his leader region, displays the typical features of the T box transcriptional attenuation mechanism which is involved in the regulation of many amino acid biosynthetic operons and tRNA synthetase genes in gram-positive bacteria. Here we describe the regulation of transcription of the his operon by the level of histidine in the growth medium. In the absence of histidine, two transcripts are present. One covers the entire operon, while the other stops at a terminator situated about 250 bp downstream of the transcription start point. DNA sequences implicated in regulation of the his operon were identified by transcriptional fusion with luciferase genes and site-directed mutagenesis. In addition to the previously defined sequences necessary for effective T-box-mediated regulation, new essential regions were identified. Eighteen percent of the positions of the hisleader region were found to differ in seven distantly related strains of L. lactis. Analysis of the variable positions supports the folding model of the central part of the his leader region. Lastly, in addition to the T-box-mediated regulation, the operon is regulated at the level of initiation of transcription, which is repressed in the presence of histidine. An operator site, necessary for full repression, overlaps the terminator involved in the T box attenuation mechanism. The functionality of the operator is altered on plasmids with low and high copy numbers, suggesting that supercoiling may play a role in the expression of the his operon. The extents of regulation at the levels of initiation and attenuation of transcription are 6- to 8-fold and 14-fold, respectively. Together, the two levels of control allow a 120-fold range of regulation of theL. lactis operon by histidine.

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Inducible gene expression and environmentally regulated genes in lactic acid bacteria

Cited by 31 publications

References 71 publications

Environmental stress responses inLactococcus lactis

Environmental stress responses inLactococcus lactis

Molecular characterization of the pH‐inducible and growth phase‐dependent promoter P170 of Lactococcus lactis

Regulation of Expression of the Lactococcus lactis Histidine Operon

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