Abstract
Organisms are assemblages of the host and their endogenous bacteria, which are defined as microbiomes. The host and its microbiome undergo a mutual evolutionary process to adapt to changes in the environment. Chironomids (Diptera; Chironomidae), are aquatic insects that grow and survive in polluted environments; however, the mechanisms that protect them under these conditions are not fully understood. Here we present evidence that the chironomids’ microbiome enables them to survival in polluted environments. It has been demonstrated that about 40% of the microbiota that inhabit Chironomus transvaalensis egg masses and larvae has the potential to detoxify different toxicants. Metagenomic analysis of Chironomus ramosus larvae demonstrated the presence of genes in the insects’ microbiome that can help the insects to survive in hostile environments. A set of experiments demonstrated that short exposure of C. transvaalensis larvae to metals significantly changed their microbiota composition in comparison to unexposed larvae. Another experiment, that followed Koch’s postulates, demonstrated that disinfected C. transvaalensis larvae can survive toxic lead and chromium exposure when they are recolonized with bacteria that can detoxify these toxic metals. This accumulating research, points to the conclusion that the chironomid microbiome plays a role in protecting its host from toxicants.
Highlights
All organisms host microbial assemblages that reside inside or on the surfaces of their body
Aeromonas species were detected in all life stages of C. transvaalensis, suggesting that chironomids are reservoirs of Aeromonas species and they may serve as symbionts (Senderovich et al, 2008; Sela et al, 2020)
To determine the role of chironomids’ endogenous bacteria in the survival of chironomids in polluted environments, a bioassay based on Koch’s postulates was performed (Figure 1; Senderovich and Halpern, 2013). They isolated two bacterial strains; Chromobacterium aquaticum and Shewanella decolorationis, that were identified from C. transvaalensis larvae that survived exposure to toxic lead and hexavalent chromium, respectively
Summary
All organisms host microbial assemblages that reside inside or on the surfaces of their body These endogenous microorganisms, and the genes that are encoded in their chromosomes, are called the microbiome. Chironomids live in almost every type of aquatic habitat and can tolerate extreme temperatures, pH, salinity, depth, current velocity and even dehydration and ultraviolet (UV) and gamma radiations (Armitage et al, 1995; Datkhile et al, 2009a,b, 2015; Thorat and Nath, 2015) As a group, they are considered pollution tolerant and are known to thrive under adverse environmental conditions (Armitage et al, 1995; Wright and Burgin, 2009). Aeromonas species were detected in all life stages of C. transvaalensis, suggesting that chironomids are reservoirs of Aeromonas species and they may serve as symbionts (Senderovich et al, 2008; Sela et al, 2020)
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