Biology subjects

Oftedal, T. F.

Publications and source records attributed to Oftedal, T. F..

3 recordsLinked to original sources

bioRxiv2026

Novel insights into the biosynthesis and diversity of leaderless multipeptide bacteriocins

Garvicin KS (GarKS) is a three-peptide, leaderless, broad-spectrum bacteriocin that is active against a wide range of Gram-positive bacteria, including several foodborne pathogens and antibiotic-resistant strains. This bacteriocin is considered a candidate for application in food preservation and medical treatments; however, key knowledge about the producer strain, regulation of production, and the mechanism of action is still lacking for leaderless, multipeptide bacteriocins, including GarKS. A hybrid sequencing strategy was used to obtain a high-quality closed genome assembly of the native GarKS producer Lactococcus garvieae KS1546, which showed that the bacteriocin was encoded on a 50 kb plasmid (pKS50). Comparative analysis with updated sequence databases indicates that the producer strain should be reclassified as Lactococcus petauri. The roles of the biosynthetic genes, putatively encoding a transcriptional regulator (gakR) and immunity protein (gakI), were examined using heterologous expression. Removal of gakR resulted in a 6-fold decrease in GarKS production, and expression of gakI caused a 250-fold decrease in susceptibility to GarKS, with varying degrees of cross-immunity to other multipeptide bacteriocins. Isolation and whole-genome sequencing of spontaneous GarKS mutants in L. lactis showed that resistance levels are low, but that ythA, a PspC-domain-containing protein involved in a phage stress response pathway is involved in the GarKS susceptible phenotype. To decipher conserved features involved in production of these bacteriocins, we finally used genome mining to identify 11 candidates for new multipeptide bacteriocins; four of them were obtained synthetically and confirmed to be bioactive peptides inhibiting important pathogens including Listeria monocytogenes and enterococci.

microbiology↗

bioRxiv2025

The phage shock protein response of Listeria monocytogenes influences tolerance to the multipeptide bacteriocin garvicin KS

An estimated 30% of all food produced worldwide is lost or wasted every year. A considerable portion of that waste is due to perishable food products, that spoil and can become unsafe to eat relatively quickly. For some high-quality perishables, such as fresh fish and cold-smoked salmon, traditional food preservation techniques are unsuitable as they can compromise sensory qualities such as flavor, texture, and freshness. These products often support the growth of the human pathogen Listeria monocytogenes, which can be present if thermal treatment is not applied. Thus, antilisterial bacteriocins like garvicin KS (GarKS) in combination with conventional technologies like high-pressure processing (HPP) or modified atmosphere packaging (MAP) are being investigated as hurdle strategies to increase the shelf life and food safety of packaged fish products. In this study we showed that L. monocytogenes strains associated with fish food and fish processing plants are susceptible to GarKS with MIC values ranging from 20 to 275 nM. Exposure to GarKS resulted in an upregulation of genes involved in the phage shock protein response, and isolation of resistant mutants indicated a low frequency of resistance to GarKS (10{square}{square} to 10{square}11). Resistant mutants were shown to harbor disruption mutations in lmo2468, encoding a PspC-domain-containing protein. Overexpression of this gene increased susceptibility to GarKS two-fold and restored wild-type susceptibility in a disruption mutant. This study identify the phage shock protein response as a key player involved in susceptibility to GarKS.

molecular biology↗

bioRxiv2024

An antibiotic-free antimicrobial combination of bacteriocins and a peptidoglycan hydrolase: in vitro and in vivo assessment of its efficacy

Mastitis is an inflammatory disease of the mammary gland commonly brought about by bac-terial pathogens that gain physical access to the glandular epithelium through the teat canal. In bovines, common mastitis-causing agents are environmental or pathogenic bacterial spe-cies, including staphylococci, streptococci, enterococci, and Gram-negative bacteria such as Escherichia coli. Current therapeutic strategies for bovine mastitis typically involve the ad-ministration of antibiotic formulations within the infected udder, possibly resulting in in-creased selection of antibiotic resistance and the accumulation of antibiotic residues within the milk. In this study, we sought to design an antibiotic-free antimicrobial formulation to treat bovine mastitis based on bacterial antimicrobial peptides (bacteriocins) and proteins (pepti-doglycan hydrolases). Using a combination of in vitro assays with a range of bacteriocins, we show that the combination of the thiopeptide micrococcin P1 (MP1) and the lantibiotic nisin A (NisA) is a robust antimicrobial formulation that effectively inhibits the growth of bo-vine mastitis-derived bacteria, both in planktonic and biofilm-associated growth modes. The addition of AuresinePlus (Aur, a staphylococcus-specific PGH) further increased the antimi-crobial potency against S. aureus. Furthermore, using two mouse models, a skin infection model and a mastitis model, we show that the combination MP1-NisA-Aur effectively inhibits methicillin-resistant S. aureus (MRSA) in vivo. We discuss the potential and challenges of using antibiotic-free antimicrobial combinations in the treatment of bacterial infections.

microbiology↗