Tamara Aleksandrzak-Piekarczyk, PhD, DScLaboratory of Applied Microbiology
The laboratory is interested in research on biodiversity of natural bacterial strains and bacteriophages, probiotic features and molecular mechanisms of bioactivity of lactic acid bacteria (LAB) on model tissue cultures and animals, identification of novel compounds with antipathogenic, antitumor and/or immune system-stimulatory activity, genetic modifications of bacteria for organic acid bioproduction, LAB plasmidomes and designing vectors for heterologous protein expression.
Main Scientific Achievements
- Among the first to discover and establish the role of the global transcriptional CcpA regulator in the regulation of sugar metabolism in Lactococcus lactis.
- First to discover an alternative pathway for lactose utilization in L. lactis.
- First to establish the role of the ClaR and GlaR regulator essential for respectively lactose/cellobiose and galactose metabolism in L. lactis.
- First to unravel the genome sequences and identifying the “probiogenomes” of three probiotic Lactobacillus strains present in the commercially available Polish probiotic supplement of antiallergic action (Latopic).
- Amongst the first to discover that mannose-specific transport system PTS is a receptor for many nonhomologous bacteriocins with different spectra of activity.
For a number of years, our studies included the molecular mechanisms of sugar metabolism in lactic acid bacteria, characterization of their plasmidomes, and more recently, the biology of toxic bacterial peptides – bacteriocins. The last subject includes studies on bacteriocin purification, functional genetics, gene regulation and quorum sensing, receptor identification, and research on their mechanisms of action and resistance development. Recently, we have focused on understanding how bacteriocins interact with receptors on target cells and how these interactions lead to bacterial destruction. Gathered knowledge is important for the development of bacteriocins for safe and effective applications, both as food preservatives and as new drugs. We are increasingly interested in applied research, particularly the development of bacteriocins as drugs to combat antibiotic-resistant pathogens and as anti-tumor agents. In our study, we identified a metal-dependent protease as a new membrane receptor that binds to non-translationally modified bacteriocins enterocin K1 and LsbB, affecting Enterococcus faecium and Lactococcus lactis. Moreover, we demonstrated that the mannose-specific phosphotransferase system (Man-PTS) is involved in the interaction of a number of structurally and functionally distinct bacteriocins, refuting the previously prevailing thesis that non-homologous bacteriocins with different activity spectra interact with distinct membrane receptors of bacterial cells. We postulate that this interaction is possible due to differences in amino acid sequence / Man-PTS structure, which determine the selectivity of binding of specific bacteriocin groups. Another necessary aspect of bacteriocin research in the context of their potential use in food industry or medicine as bactericides, is the analysis of resistance induction among susceptible strains. We have shown that the presence of bacteriocins can induce mutations in four-component systems, resulting in increased resistance (so-called gain-of-function mutations). These mutations also lead to cross-resistance to peptide antibiotics, but in some cases have the opposite effect, leading to susceptibility of the strain to the antibiotic. We are currently investigating the molecular basis of this interesting phenomenon.
Our research concerns broadly understood molecular microbiology, biochemical and genetic mechanisms related to the probiotic features in bacteria and their influence on higher organisms. These interests are primarily in the area of physiological and genetic characterization and probiotic properties of newly isolated environmental strains of lactic acid bacteria, including their ability to metabolize saccharides, adherence to biotic and abiotic surfaces, resistance to salinity and acidification, bacteriocin production and antimicrobial activity, antibiotic resistance, and genetic identification of bacteria isolated from animal gastrointestinal tracts. As a result of this work, we have identified Lactobacillus strains with anti-Campylobacter activity, strong adherence and survival in the chicken intestine after in ovo administration, Lactococcus lactis carrying plasmids with tetracycline resistance genes, which we are currently using to construct a unique expression vector. By qRT-PCR we estimated the presence of three Lactobacillus strains derived from a Polish probiotic preparation in the mouse intestine, which, in addition to a number of other studies, allowed us to attribute to particular strains a positive effect on the integrity of enterocytes and, consequently, the silencing of allergic reactions. Our interest in the genetic aspects of strain adherence has resulted in several papers, among which two describe plasmids as a source of unique genes encoding proteins involved in adhesion, and another characterizes the genetic determinants affecting high adherence in bacteria isolated from different environments.
- High throughput screening test for bacteriocins targeting pathogens of interes (our main pathogens of interest are MRSA, VRE and Listeria).
- Well-developed platform to study bacteriocins, including both biochemical, genetic, structural and mode of action studies, biofilm formation and anti-biofilm antimicrobials.
- Phenotypic Microarray Facility on the phenomic characterization of individual bacterial strains, microbial consortia, and cell lines.
- Lactococcus lactis resistance to aureocin A53- and enterocin L50-like bacteriocins and membrane-targeting peptide antibiotics relies on the YsaCB-KinG-LlrG four-component system. Tymoszewska A, Kirill V. Ovchinnikov KV, Dzung DB, Slodownik M, Maron E, Beatriz Martínez, and Aleksandrzak-Piekarczyk T*(corresponding author). Antimicrobial Agents and Chemotherapy. 2021. DOI: 3390/ijms22031014
- The extracellular loop of Man-PTS subunit IID is responsible for the sensitivity of Lactococcus garvieae to garvicins A, B and C. Tymoszewska A, Diep DB, Aleksandrzak-Piekarczyk T* (corresponding author). Scientific Reports. 2018. DOI: s41598-018-34087-2
- The non-lantibiotic bacteriocin Garvicin Q targets Man-PTS in a broad spectrum of sensitive bacterial genera. Tymoszewska A, Diep DB, Wirtek P, Aleksandrzak-Piekarczyk T* (corresponding author). 2017. DOI: s41598-017-09102-7
- Genomic and functional characterization of the unusual pLOCK 0919 plasmid harboring the spaCBA pili cluster in Lactobacillus casei LOCK 0919. Aleksandrzak-Piekarczyk T* (corresponding author), Koryszewska-Bagińska A, Grynberg M, Nowak A, Cukrowska B, Kozakova H, Bardowski J. 2016. DOI: academic.oup.com/gbe/article/8/1/202/2574160
- New synthetic genes encoding peptide fragments of natural myelin proteins containing nucleotide sequence encoding fragment of myelin protein having specific amino acid/nucleotide sequences, useful for induction of oral tolerance. European patent awarded in January 2016. Patent no: WO2013104424-A1
- Dzung Bao Diep, University of Life Sciences, Norway, https://www.nmbu.no/ans/dzung.diep
- Lidia Stasiak-Rożańska, Warsaw University of Life Sciences, Poland