Unlike mammals, crustaceans have bacteria colonization in their hemolymph, the origin of hemolymph bacteria and their role in crayfish survival aroused our interest. We observed that Vibrio significantly enhanced the load of hemolymph bacteria in Procambarus clarkii. Vibrio specifically degrades peritrophins-44 in crustaceans via the secreted protease of C1 esterase (StcE). Crayfish expression of the protease inhibitor (inter-α-trypsin inhibitor heavy chain 4 , ITIH4), inhibiting the enzymatic activity of StcE. Interestingly, the crayfish exhibits a relatively high tolerance to heavy metals. The Exiguobacterium, the symbiotic bacteria in the hemolymph of P. clarkii, were proved to be primary contributor to Cr(VI) tolerance. Further investigation suggested that it resists Cr(VI) through the activation of the ABC transporter system and the reduction of Cr(VI) via the reductase gene nfsA. Bacteria colonize the crayfish’s hemolymph during its development. And the bacteria in hemolymph achieve a dynamic balance with the crayfish, helping the crayfish adapt to the water environment.
Keywords: Hemolymph bacteria, Exiguobacterium, Vibrio, Procambarus clarkii