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

Abstract

Chironomids (Diptera; Chironomidae) are aquatic insects that are abundant in freshwater. We aimed to study the endogenous microbiota composition of Chironomus ramosus larvae that were sampled from the Mutha River and a laboratory culture in India. Furthermore, we performed a metagenomic analysis of the larval microbiome, sampled from the Mutha River. Significant differences were found between the bacterial community composition of C. ramosus larvae that were sampled from the Mutha River and the laboratory culture. A total of 54.7% of the amplicon sequence variants (ASVs) that were identified in the larvae from the Mutha River were unique, compared to only 12.9% of unique ASVs that were identified from the laboratory-reared larvae. The four most abundant phyla across all samples were: Proteobacteria, Fusobacteria, Firmicutes, and Bacteroidetes, while the nine most abundant genera were: Aeromonas, Alkanindiges, Breznakia, Cetobacterium, Chryseobacterium, Desulfovibrio, Dysgonomonas, Thiothrix, and Vibrio. Moreover, in the metagenomic analysis, we detected bacterial genes and bacterial pathways that demonstrated the ability to degrade different toxic compounds, detoxify metal, and confer resistance to antibiotics and UV radiation, amongst other functions. The results illuminate the fact that there are detoxifying enzymes in the C. ramosus larval microbiome that possibly play a role in protecting the insect in polluted environments.

The Chironomid Microbiome Plays a Role in Protecting Its Host From Toxicants

“…Remarkably, high abundances of Acinetobacter and Pseudomonas were identified in C. ramosus larvae (Sela et al, 2021). These data provided evidence for the ability of the C. ramosus microbiome to protect the insect in hostile environments (Sela et al, 2021).…”

“…Furthermore, the presence of genes for resistance to antibiotics, UV radiation and others that were related to stress tolerance were also identified in the C. ramosus larval microbiome. Overall, 115,959 bacterial functional genes and 445 different pathways were detected in the C. ramosus larval microbiome (Sela et al, 2021). One of the pathways that was detected in the larval microbiome was the toluene degradation pathway.…”

“…It was found that species of Bacillus and Pseudomonas genera are able to degrade toluene and use it as their sole carbon source (Hamzah et al, 2011). These genera were identified in C. ramosus metagenomic analysis (Sela et al, 2021). Another relevant pathway identified is the atrazine degradation pathway (Sela et al, 2021).…”

“…These genera were identified in C. ramosus metagenomic analysis (Sela et al, 2021). Another relevant pathway identified is the atrazine degradation pathway (Sela et al, 2021). Atrazine is herbicide (Steinberg et al, 1995) extensively used to prevent the growth of wild plants in agriculture worldwide (Graymore et al, 2001).…”

Comparative Microbiota Composition Across Developmental Stages of Natural and Laboratory-Reared Chironomus circumdatus Populations From India

“…The high abundance of this genus in the larvae is more pronounced when it is compared to its abundance in the egg mass and pupa life stages (nearly absent, in all habitats) (Table 2). Similarly, Cetobacterium was highly abundant in C. ramosus larval microbiota that were sampled from the Mutha River (39.9%) while its abundance in laboratory culture was reduced to 3.3% (Sela et al, 2021). This suggests that Cetobacterium has a role in the larval survival in the river.…”