Biology subjects

Mickiewicz, K.

Publications and source records attributed to Mickiewicz, K..

3 recordsLinked to original sources

bioRxiv2024

The last resort antibiotic daptomycin exhibits two independent antibacterial mechanisms of action

Daptomycin is a lipopeptide antibiotic, commonly used as last resort treatment against multidrug resistant Gram-positive pathogens. Despite its clinical success, the mechanism through which daptomycin exerts its antibacterial properties has remained controversial. Much of the debate is focused around daptomycins ability to depolarise the cytoplasmic membrane, potential formation of large membrane pores, and its more recently discovered capability to inhibit cell wall synthesis and disturb membrane lipid domain organisation through interactions with cell wall precursor lipids. Here we show that, rather than representing different facets of a single underlying activity, daptomycin exhibits two independent antibacterial mechanisms of action: (i) targeting of cell wall precursor lipids that leads to cell wall synthesis inhibition and (ii) membrane depolarisation that does not rely on interactions with cell wall precursor lipids. This dual mechanism of action provides an explanation for the frequently disagreeing findings obtained through in vivo and in vitro studies and explains why resistance development towards daptomycin is slow and multifactorial. In a broader context, this demonstrates that dual mechanism antibiotics can be clinically successful and exhibit favourable characteristics in terms of real-world, clinically relevant resistance development.

microbiology↗

bioRxiv2024

Conflicts between the DNA replication and repair machineries promote cell death in Gram-positive bacteria

Cellular proliferation relies on successful coordination and completion of genome replication and segregation. To help achieve this, many bacteria utilise regulatory pathways that ensure DNA replication initiation only occurs once per cell cycle. When dysregulated, loss of DNA replication control can have severe consequences. In Escherichia coli it has been established that hyper-initiation of DNA synthesis leads to pleiotropic genome instability and cell death. Therefore, targeting DNA replication initiation proteins to promote hyper-initiation may be an approach to generate novel antimicrobials. However, the pathways and potential consequences of replication hyper-initiation in Gram-positive species remain enigmatic. To address this question, we devised genetic systems to artificially induce hyper-initiation in the model organism Bacillus subtilis and the pathogen Staphylococcus aureus. In both species, hyper-initiation elicited cellular degeneration culminating in growth inhibition by cell death. During this process in B. subtilis, temporal analyses revealed the early onset of the DNA damage response, followed by membrane depolarisation and cell lysis. This phenotype could be supressed by removing pathways that repair damaged DNA, suggesting that cell death is a consequence of conflicts between DNA replication and repair. In S. aureus, cells quickly accumulated striking morphological changes associated with rapid loss of chromosomal DNA and death via a lysis-independent pathway. Moreover, inducing hyper-initiation in S. aureus was observed to decrease bacterial survival during infection of murine macrophages. Taken together, the data suggest that stimulating initiation of bacterial DNA synthesis could be an alternative approach to inhibiting microbial growth, particularly in combination with compounds that inhibit or poison DNA repair, akin to cancer therapies.

microbiology↗

bioRxiv2021

L-form switching confers antibiotic, phage and stress tolerance in pathogenic Escherichia coli

The bacterial L-form is induced by exposure to cell wall targeting antibiotics or innate immune effectors such as lysozyme and is likely to be important in many human infections. Here, we demonstrate that the osmotically fragile L-form is a distinct physiological state in Escherichia coli that is highly tolerant of oxidative stress and resistant to powerful antibiotics and common therapeutic bacteriophages. L-forms quickly revert (<20h) to their cell-walled state after antibiotic withdrawal, with apparently normal physiology and with few or no changes in DNA sequence. T4-like phages that are obligately lytic in cell-walled E. coli preferentially pseudolysogenise their L-forms providing them with transient superinfection immunity. Our data indicate that L-form switching is a common response of pathogenic E. coli strains to cell wall-targeting antibiotics and that the most commonly used lytic bacteriophages are ineffective against them in this state.

microbiology↗