Unlocking the bio-shield: adaptive metal tolerance of aquatic insect-associated bacteria

Background: Aquatic insects are known to host diverse microbial communities that may play important

roles in environmental adaptation and bioremediation processes. It has been demonstrated that bacteria

associated with aquatic organisms can develop tolerance to heavy metals present in contaminated aquatic

ecosystems.

Aim: The objective of the present study was to undertake a preliminary screening of heavy metal-resistant

bacteria that had been isolated from an aquatic insect. Hydrobius fuscipes (Linnaeus, 1758) was selected as the

study's prototype. This species is easy to identify and is found in aquatic environments.

Materials and methods: In order to isolate bacteria, it was necessary to sterilize the insect surface in order

to eliminate external contaminants. The specimen was then homogenized in a sterile physiological saline

solution. From the homogenate, 100 µL was spread onto Tryptic Soy Agar (TSA) plates and incubated to obtain

bacterial colonies. A total of seven bacterial isolates were obtained.

Results: The Gram staining results indicated that three isolates were Gram-positive, while four isolates were

Gram-negative. The resistance of these isolates to heavy metals was evaluated using culture media that had

been supplemented with zinc (Zn+

), cadmium (Cd++) and lead (Pb++). Preliminary observations indicated that

at least one Gram-positive and one Gram-negative isolate were able to grow in the presence of 200 µM

concentrations of these metals, suggesting potential tolerance to heavy metal stress.

Conclusion: These findings suggest that bacteria associated with aquatic insects may possess adaptive

mechanisms that enable survival under metal stress conditions. These microorganisms have the potential to

serve as valuable subjects in further studies on heavy metal resistance and potential applications in

bioremediation.