Biology subjects

Kanarek, K.

Publications and source records attributed to Kanarek, K..

4 recordsLinked to original sources

bioRxiv2025

Phage-encoded homing endonucleases attenuate bacterial immunity

The arms race between bacteria and bacteriophages (phages) gave rise to multiple layers of antagonistic mechanisms, many of which remain unexplored. Here, we investigated the anti-phage defense system GAPS4 and showed that it is a non-selective DNase triggered by sensing DNA breaks. We further demonstrated that this activation mechanism renders GAPS4 a double-edged sword, sensitizing bacteria to various forms of antibacterial antagonism. Using comparative genomics, we found that phage-encoded homing endonucleases, long considered selfish mobile genetic elements, enhance phage fitness by attenuating GAPS4-mediated immunity. Our findings shed light on the evolutionary advantage provided by these ubiquitous mobile elements to their host phages, and on the intricate evolutionary cross-talk between bacteria and their predators.

microbiology↗

bioRxiv2025

Assessing toxicity and competitive fitness of vibrios isolated from coastal waters in Israel

Several species of aquatic bacteria belonging to the genus Vibrio are emerging pathogens of humans and marine animals. Vibrio-associated infections have been shown to correlate with the increase in the oceans surface water temperatures. A slow yet steady increase in vibrios isolated from clinical settings in Israel over the past decade led us to investigate the pathogenic potential of vibrios in Israels coastal waters. We isolated and sequenced the genomes of 23 vibrios from the Mediterranean and the Red Sea. Analysis of these genomes revealed the presence of diverse toxin secretion systems and toxins, as well as mobile genetic elements known to facilitate the dissemination of fitness-enhancing determinants. Moreover, we showed that at least 10 of these isolates can induce cell death in bone marrow-derived macrophages and that at least 12 isolates can intoxicate a rival Vibrio strain in interbacterial competition. Lastly, we determined the susceptibility profiles of these isolates to common antibiotics used to treat Vibrio infections and found widespread resistance to azithromycin. Taken together, our results reveal pathogenic potential within the Vibrio population of Israels coastal waters and underline the need for continued environmental monitoring of emerging pathogens. ImportanceThe oceans surface water temperatures have increased in past decades due to climate change. This increase correlates with the spread of vibrios, a genus of aquatic bacteria, many of which are pathogens of humans and marine animals. Since Vibrio-associated illnesses are rising in Israel, we set out to investigate the Vibrio population in Israels coastal environments and monitor their pathogenic potential. We found diverse repertoires of predicted toxins, the ability to kill mammalian immune cells, and traits that enhance bacterial fitness, such as antibacterial toxicity and resistance to antibiotics commonly used to treat Vibrio infections. These findings indicate that pathogenic traits are circulating within the environmental Vibrio population in Israels coastal waters and suggest that continued monitoring is essential to identify emerging pathogenic strains.

microbiology↗

bioRxiv2023

A widespread bacterial mobile genetic element encodes weapons against phages, bacteria, and eukaryotes

Conflicts between bacteria and their rivals led to an evolutionary arms race and the development of bacterial immune systems. Although diverse immunity mechanisms were recently identified, many remain unknown, and their dissemination within bacteria is poorly understood. Here, we describe a widespread genetic element, defined by the presence of the Gamma-Mobile-Trio (GMT) proteins, that serves as a bacterial survival kit. We show that GMT-containing genomic islands are active mobile elements with cargo comprising various anti-phage defense systems, in addition to antibacterial type VI secretion system (T6SS) effectors and antibiotic resistance genes. We identify four new anti-phage defense systems encoded within GMT islands. A thorough investigation of one system reveals that it is triggered by a phage capsid protein to induce cell dormancy. Our findings underscore the need to broaden the concept of defense islands to include also antibacterial offensive tools, such as T6SS effectors, as they share the same mobile elements as defensive tools for dissemination.

microbiology↗

bioRxiv2022

A new class of polymorphic T6SS effectors and tethers

Bacteria use the type VI secretion system (T6SS) to deliver toxic effectors into bacterial or eukaryotic cells during interbacterial competition, host colonization, or when resisting predation. The identity of many effectors remains unknown. Here, we identify RIX, a new domain that defines a class of polymorphic T6SS cargo effectors. RIX, which is widespread in the Vibrionaceae family, is located at N-termini of proteins containing diverse antibacterial and anti-eukaryotic toxin domains. We demonstrate that RIX-containing proteins are delivered via T6SS into neighboring cells, and that RIX is necessary and sufficient for secretion. We show that RIX-containing proteins can also act as tethers, enabling the T6SS-mediated delivery of other cargo effectors by a previously undescribed mechanism. RIX-containing proteins significantly enlarge the repertoire of known T6SS effectors, especially those with anti-eukaryotic activities. Our findings also suggest that T6SSs may play a major, currently underappreciated, role in interactions between vibrios and eukaryotes.

microbiology↗