Quorum‐sensing signaling by chironomid egg masses’ microbiota, affects haemagglutinin/protease (HAP) production by Vibrio cholerae

Abstract

Vibrio cholerae, the causative agent of cholera, is commonly isolated, along with other bacterial species, from chironomid insects (Diptera: Chironomidae). Nevertheless, its prevalence in the chironomid egg masses’ microbiota is less than 0.5%. V. cholerae secretes haemagglutinin/protease (HAP) that degrades the gelatinous matrix of chironomid egg masses and prevents hatching. Quorum sensing (QS) activates HAP production in response to accumulation of bacterial autoinducers (AIs). Our aim was to define the impact of chironomid microbiota on HAP production by V. cholerae. To study QS signaling, we used V. cholerae bioluminescence reporter strains (QS‐proficient O1 El‐Tor wild‐type and QS‐deficient mutants) and different bacterial species that we isolated from chironomid egg masses. These egg mass isolates, as well as a synthetic AI‐2, caused an enhancement in lux expression by a V. cholerae QS‐deficient mutant. The addition of the egg mass bacterial isolate supernatant to the QS‐deficient mutant also enhanced HAP production and egg mass degradation activities. Moreover, the V. cholerae wild‐type strain was able to proliferate using egg masses as their sole carbon source, while the QS‐deficient was not. The results demonstrate that members of the chironomid bacterial consortium produce external chemical cues that, like AI‐2, induce expression of the hapA gene in V. cholerae. Understanding the interactions between V. cholerae and the insects’ microbiota may help uncover the interactions between this pathogen and the human gut microbiota.

Changes in Microbiota Composition Along the Metamorphosis Developmental Stages of Chironomus transvaalensis

“…Vibrio cholerae degrades the egg masses' glycoprotein matrix by secreting haemagglutinin protease, while Aeromonas degrades chitin by secreting chitinases. This egg mass degradation prevents larval hatching and thus, controls chironomid population levels on the one hand (Halpern, 2010) and may support the maintenance of the egg mass's endogenous bacterial communities, on the other hand, by supplying them with available nutrients Sela et al, 2020). Thus, the presence of V. cholerae and Aeromonas species in all four life stages of C. transvaalensis might represent a mutualistic relationship between these species and their natural host.…”

Chironomus ramosus Larval Microbiome Composition Provides Evidence for the Presence of Detoxifying Enzymes

“…In a recent study, almost half of the microbial community that was identified in C. transvaalensis egg masses belonged to bacterial genera that might have the ability to protect the insect under stress conditions [ 11 ]. The first instar larva feeds on the egg mass remains which contain both nutrients and endogenous microorganisms [ 12 ]. It is hypothesized that the microbiota that inhabits the egg mass protects the insect along its metamorphosis [ 11 ].…”

A New Contact Killing Toxin Permeabilizes Cells and Belongs to a Broadly Distributed Protein Family

“… Vibrio cholerae is a wide-spread gastrointestinal pathogen that has caused seven cholera pandemics ( 22 ). The bacterium is found in polymicrobial marine ecosystems in association with copepods, fish, and insects ( 23 – 25 ). V. cholerae employs T6SS effectors that disrupt cell envelopes and contribute to pathogenicity in hosts ( 26 – 33 ).…”