Dataset Information

Genome adaptive evolution of Lactobacillus casei under long-term antibiotic selection pressures.

ABSTRACT: The extensive use of antibiotics in medicine has raised serious concerns about biosafety. However, the effect of antibiotic application on the adaptive evolution of microorganisms, especially to probiotic bacteria, has not been well characterized. Thus, the objective of the current work was to investigate how antibiotic selection forces might drive genome adaptation using Lactobacillus (L.) casei Zhang as a model.Two antibiotics, amoxicillin and gentamicin, were consistently applied to the laboratory culture of L. casei Zhang. We then monitored the mutations in the bacterial genome and changes in the minimum inhibitory concentrations (MICs) of these two antibiotics along a 2000-generation-cultivation lasted over 10 months.We found an approximately 4-fold increase in the genome mutation frequency of L. casei Zhang, i.e. 3.5?×?10-9 per base pair per generation under either amoxicillin or gentamicin stress, when compared with the parallel controls grown without application of any antibiotics. The increase in mutation frequency is significantly lower than that previously reported in Escherichia (E.) coli. The rate of de novo mutations, i.e. 20 per genome, remained low and stable throughout the long-term cultivation. Moreover, the accumulation of new mutations stopped shortly after the maximum bacterial fitness (i.e. the antibiotic MICs) was reached.Our study has shown that the probiotic species, L. casei Zhang, has high genome stability even in the presence of long-term antibiotic stresses. However, whether this is a species-specific or universal characteristic for all probiotic bacteria remains to be explored.

SUBMITTER: Wang J

PROVIDER: S-EPMC5402323 | biostudies-literature | 2017 Apr

REPOSITORIES: biostudies-literature

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Genome adaptive evolution of Lactobacillus casei under long-term antibiotic selection pressures.

Wang Jicheng J Dong Xiao X Shao Yuyu Y Guo Huiling H Pan Lin L Hui Wenyan W Kwok Lai-Yu LY Zhang Heping H Zhang Wenyi W

BMC genomics 20170424 1

<h4>Background</h4>The extensive use of antibiotics in medicine has raised serious concerns about biosafety. However, the effect of antibiotic application on the adaptive evolution of microorganisms, especially to probiotic bacteria, has not been well characterized. Thus, the objective of the current work was to investigate how antibiotic selection forces might drive genome adaptation using Lactobacillus (L.) casei Zhang as a model.<h4>Methods</h4>Two antibiotics, amoxicillin and gentamicin, wer ...[more]

PMID: 28438179

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Project description:This study explored transient inactivation of the gene encoding the DNA mismatch repair enzyme MutS as a tool for adaptive evolution of Lactobacillus casei MutS deletion derivatives of L. casei 12A and ATCC 334 were constructed and subjected to a 100-day adaptive evolution process to increase lactic acid resistance at low pH. Wild-type parental strains were also subjected to this treatment. At the end of the process, the ΔmutS lesion was repaired in representative L. casei 12A and ATCC 334 ΔmutS mutant isolates. Growth studies in broth at pH 4.0 (titrated with lactic acid) showed that all four adapted strains grew more rapidly, to higher cell densities, and produced significantly more lactic acid than untreated wild-type cells. However, the adapted ΔmutS derivative mutants showed the greatest increases in growth and lactic acid production. Further characterization of the L. casei 12A-adapted ΔmutS derivative revealed that it had a significantly smaller cell volume, a rougher cell surface, and significantly better survival at pH 2.5 than parental L. casei 12A. Genome sequence analysis confirmed that transient mutS inactivation decreased DNA replication fidelity in both L. casei strains, and it identified genetic changes that might contribute to the lactic acid-resistant phenotypes of adapted cells. Targeted inactivation of three genes that had acquired nonsense mutations in the adapted L. casei 12A ΔmutS mutant derivative showed that NADH dehydrogenase (ndh), phosphate transport ATP-binding protein PstB (pstB), and two-component signal transduction system (TCS) quorum-sensing histidine protein kinase (hpk) genes act in combination to increase lactic acid resistance in L. casei 12A.IMPORTANCE Adaptive evolution has been applied to microorganisms to increase industrially desirable phenotypes, including acid resistance. We developed a method to increase the adaptability of Lactobacillus casei 12A and ATCC 334 through transient inactivation of the DNA mismatch repair enzyme MutS. Here, we show this method was effective in increasing the resistance of L. casei to lactic acid at low pH. Additionally, we identified three genes that contribute to increased acid resistance in L. casei 12A. These results provide valuable insight on methods to enhance an organism's fitness to complex phenotypes through adaptive evolution and targeted gene inactivation.

Dataset Information

Genome adaptive evolution of Lactobacillus casei under long-term antibiotic selection pressures.

Publications

Genome adaptive evolution of Lactobacillus casei under long-term antibiotic selection pressures.

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