Dataset Information

Disruption of a Transcriptional Repressor by an Insertion Sequence Element Integration Leads to Activation of a Novel Silent Cellobiose Transporter in Lactococcus lactis MG1363.

ABSTRACT: Lactococcus lactis subsp. cremoris strains typically carry many dairy niche-specific adaptations. During adaptation to the milk environment these former plant strains have acquired various pseudogenes and insertion sequence elements indicative of ongoing genome decay and frequent transposition events in their genomes. Here we describe the reactivation of a silenced plant sugar utilization cluster in an L. lactis MG1363 derivative lacking the two main cellobiose transporters, PtcBA-CelB and PtcBAC, upon applying selection pressure to utilize cellobiose. A disruption of the transcriptional repressor gene llmg_1239 by an insertion sequence (IS) element allows expression of the otherwise silent novel cellobiose transporter Llmg_1244 and leads to growth of mutant strains on cellobiose. Llmg_1239 was labeled CclR, for cellobiose cluster repressor.IMPORTANCE Insertion sequences (ISs) play an important role in the evolution of lactococci and other bacteria. They facilitate DNA rearrangements and are responsible for creation of new genetic variants with selective advantages under certain environmental conditions. L. lactis MG1363 possesses 71 copies in a total of 11 different types of IS elements. This study describes yet another example of an IS-mediated adaptive evolution. An integration of IS981 or IS905 into a gene coding for a transcriptional repressor led to activation of the repressed gene cluster coding for a plant sugar utilization pathway. The expression of the gene cluster allowed assembly of a novel cellobiose-specific transporter and led to cell growth on cellobiose.

SUBMITTER: Solopova A

PROVIDER: S-EPMC5691405 | biostudies-literature | 2017 Dec

REPOSITORIES: biostudies-literature

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Disruption of a Transcriptional Repressor by an Insertion Sequence Element Integration Leads to Activation of a Novel Silent Cellobiose Transporter in Lactococcus lactis MG1363.

Solopova Ana A Kok Jan J Kuipers Oscar P OP

Applied and environmental microbiology 20171116 23

Lactococcus lactis subsp. cremoris strains typically carry many dairy niche-specific adaptations. During adaptation to the milk environment these former plant strains have acquired various pseudogenes and insertion sequence elements indicative of ongoing genome decay and frequent transposition events in their genomes. Here we describe the reactivation of a silenced plant sugar utilization cluster in an L. lactis MG1363 derivative lacking the two main cellobiose transporters, ...[more]

PMID: 28970222

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Project description:This study describes a transcriptome-phenotype matching approach in which the starter L. lactis MG1363 was fermented under a variety of conditions that differed in the levels of oxygen and/or salt, as well as the fermentation pH and temperature. Samples derived from these fermentations in the exponential phase of bacterial growth were analyzed by full-genome transcriptomics and the assessment of heat and oxidative stress phenotypes. Variations in the fermentation conditions resulted in up to 1000-fold differences in survival during heat and oxidative stress. More specifically, aeration during fermentation induced protection against heat stress, whereas a relatively high fermentation temperature resulted in enhanced robustness towards oxidative stress. Concomitantly, oxygen levels and fermentation temperature induced differential expression of markedly more genes when compared with the other fermentation parameters. Correlation analysis of robustness phenotypes and gene expression levels revealed transcriptome signatures for oxidative and/or heat stress survival, including the metC-cysK operon involved in methionine and cysteine metabolism. To validate this transcriptome-phenotype association we grew L. lactis MG1363 in the absence of cysteine which led to enhanced robustness towards oxidative stress. Conclusions Overall, we demonstrated the importance of careful selection of fermentation parameters prior to industrial processing of starter cultures. Furthermore, established stress genes as well as novel genes were associated with robustness towards heat and/or oxidative stress. Assessment of the expression levels of this group of genes could function as an indicator for enhanced selection of fermentation parameters resulting in improved robustness during spray drying. The increased robustness after growth without cysteine appeared to confirm the role of expression of the metC-cysK operon as an indicator of robustness and suggests that sulfur amino acid metabolism plays a pivotal role in oxidative stress survival.

Dataset Information

Disruption of a Transcriptional Repressor by an Insertion Sequence Element Integration Leads to Activation of a Novel Silent Cellobiose Transporter in Lactococcus lactis MG1363.

Publications

Disruption of a Transcriptional Repressor by an Insertion Sequence Element Integration Leads to Activation of a Novel Silent Cellobiose Transporter in Lactococcus lactis MG1363.

Similar Datasets

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