The role of chitinolytic bacteria and fungi in biodegradation of crustacean remains in lacustrine habitats

This study presents results of research on occurrence of chitinolytic bacteria and fungi in water, bottom sediments, and watershed soil of an eutrophic lake and on their ability to use the crustacean skeletons (shrimp waste) as a respiration substrate. It was found that the respiration rate of bacteria and fungi during decomposition of chitin varied in different environments. The participation of chitinolytic microorganisms in water (13%) and soil (18%) was greater than in bottom sediments (5%). The respiration activity in the presence of all parts of shrimp waste and shrimp exoskeletons observed in chitinolytic bacteria was higher than that of fungi. But fungi demonstrated the highest metabolic activity in the presence of the shrimp head sections. The highest respiration activity was observed in planktonic and soil bacteria, while the lowest, in benthic strains. The chitinolytic bacteria used well all examined respiration substrates (all parts of shrimp waste – 671 mg O₂ r⁻¹ protein in 5 days, the shrimp head sections – 851 mg O₂ r⁻¹ protein in 5 days and shrimp exoskeletons – 490 mg O₂ r⁻¹ protein in 5 days). No significant differences in respiration activity were observed in chitinolytic fungi isolated from water, bottom sediments and soil. All of fungal strains demonstrated the highest metabolic activity in the presence of the shrimp head sections (average 1083 mg O₂ r⁻¹ protein in 5 days). Shrimp exoskeletons were oxidized the least efficiently (average 160 mg O₂ r⁻¹ protein in 5 days). Certain strains were not using them at all.