News Update on Lactococcus lactis Research: Jan – 2020

Treatment of Murine Colitis by Lactococcus lactis Secreting Interleukin-10

The cytokine interleukin-10 (IL-10) has shown promise in clinical trials for treatment of inflammatory bowel disease (IBD). Using two mouse models, we show that the therapeutic dose of IL-10 are often reduced by localized delivery of a bacterium genetically engineered to secrete the cytokine. Intragastric administration of IL-10–secretingLactococcus lactis caused a 50% reduction in colitis in mice treated with dextran sulfate sodium and prevented the onset of colitis in IL-10−/− mice. This approach may cause better methods for cost-effective and long-term management of IBD in humans. [1]

The Complete Genome Sequence of the Lactic Acid Bacterium Lactococcus lactis ssp. lactis IL1403

Lactococcus lactis may be a nonpathogenic AT-rich gram-positive bacterium closely associated with the genus Streptococcus and is that the most ordinarily used cheese starter. it’s also the best-characterized carboxylic acid bacterium. We sequenced the genome of the laboratory strain IL1403, employing a novel two-step strategy that comprises diagnostic sequencing of the whole genome and a shotgun polishing step. The genome contains 2,365,589 base pairs and encodes 2310 proteins, including 293 protein-coding genes belonging to 6 prophages and 43 insertion sequence (IS) elements. Nonrandom distribution of IS elements indicates that the chromosome of the sequenced strain could also be a product of recent recombination between two closely related genomes. an entire set lately competence genes is present, indicating the power of L. lactis to undergo DNA transformation. Genomic sequence revealed new possibilities for fermentation pathways and for aerobic respiration. [2]

Physiological function of exopolysaccharides produced by Lactococcus lactis

The physiological function of EPS produced by Lactococcus lactis was studied by comparing the tolerance of the non-EPS producing strain L. lactis ssp. cremoris MG1614 and an EPS producing isogenic variant of this strain to many anti-microbial factors. There was no difference within the sensitivity of the strains to increased temperatures, freezing or freeze-drying and therefore the antibiotics, penicillin and vancomycin. A model system showed that EPS production didn’t affect the survival of L. lactis during passage through the alimentary canal although the EPS itself wasn’t degraded during this passage. The presence of cell associated EPS and EPS in suspension resulted in an increased tolerance to copper and nisin. Furthermore, cell associated EPS also protected the bacteria against bacteriophages and therefore the cell membrane degrading enzyme lysozyme. [3]

Enhance nisin yield via improving acid-tolerant capability of Lactococcus lactis F44

Traditionally, nisin was produced industrially by using Lactococcus lactis within the neutral fermentation process. However, nisin showed higher activity within the acidic environment. the way to balance the pH value for bacterial normal growth and nisin activity could be the key problem. during this study, 17 acid-tolerant genes and 6 carboxylic acid synthetic genes were introduced in L. lactis F44, respectively. Comparing to the 2810 IU/mL nisin yield of the first strain F44, the nisin titer of the engineered strains over-expressing hdeAB, ldh and murG, increased to 3850, 3979 and 4377 IU/mL, respectively. These engineered strains showed more stable intracellular pH value during the fermentation process. [4]

An Effective Cloning, Heterologous Expression and Physiological Activity in Lactococcus lactis NZ9000 of Catalase Gene from Escherichia coli DH5α

In order to clone active Catalase gene from bacteria, we introduced a way of shotgun integrating specific screen from Escherichia coli DH 5a. Genome DNA was extracted from E. coli DH5 and partially digested with Sau3AI. Then some fragments quite 2.26kb were collected and ligated with T4 DNA ligase into the BamHI-cleaved plasmid pUC18 and transformed competent E. coli TG1 cells. The transforments were incubated anaerobically on brain heart infusion (BHI) containing tannin . the tactic could detect catalase activity and screen the catalase-positive clones. The catalase protein are often identified by SDS-PAGE. The results showed that the recombinant plasmid pUC18-kat was constructed successfully by PCR identification and restriction endonuclease digestion. [5]

Reference

[1] Steidler, L., Hans, W., Schotte, L., Neirynck, S., Obermeier, F., Falk, W., Fiers, W. and Remaut, E., 2000. Treatment of murine colitis by Lactococcus lactis secreting interleukin-10. Science, 289(5483), (Web Link)

[2] Bolotin, A., Wincker, P., Mauger, S., Jaillon, O., Malarme, K., Weissenbach, J., Ehrlich, S.D. and Sorokin, A., 2001. The complete genome sequence of the lactic acid bacterium Lactococcus lactis ssp. lactis IL1403. Genome research, 11(5), (Web Link)

[3] Looijesteijn, P.J., Trapet, L., de Vries, E., Abee, T. and Hugenholtz, J., 2001. Physiological function of exopolysaccharides produced by Lactococcus lactis. International journal of food microbiology, 64(1-2), (Web Link)

[4] Enhance nisin yield via improving acid-tolerant capability of Lactococcus lactis F44
Jian Zhang, Qinggele Caiyin, Wenjing Feng, Xiuli Zhao, Bin Qiao, Guangrong Zhao & Jianjun Qiao
Scientific Reports volume 6, (Web Link)

[5] Li, C., Li, S., Li, C., Liu, Y. and Feiyun, G. (2017) “An Effective Cloning, Heterologous Expression and Physiological Activity in Lactococcus lactis NZ9000 of Catalase Gene from Escherichia coli DH5α”, Journal of Advances in Microbiology, 6(3), (Web Link)

Leave a Reply

Your email address will not be published. Required fields are marked *