The Impact of Passage Through the Intestine of the Earthworm Aporrectodea Caliginosa on the Bacterial Community

Abstract

Ecophysiological features of the transit (passed through the intestinal lacune) bacterial hydrolytic complex Aporrectodea caliginosa were studied: a comparison of biodiversity was made in the soil and coprolites, the prevailing ecological strategy and physiological states among its members. The study was conducted by a complex structural and functional method based on the succession kinetic analysis of initiated hydrolytic bacterial communities that occur after the inoculation of a set of selective liquid nutrient media with a suspension of the test samples. In addition to hydrolytic microorganisms, non-hydrolytic bacterial satellites (oligotrophs and copyotropes) are included in initiated communities. The growth of initiated bacterial communities on eight media with biopolymers (chitin, cellulose, pectin, starch, xylan, dextran 500, tween 20, casein) was measured by optical density. It was described by two kinetic parameters used to describe the pure cultures of microorganisms: the maximum specific growth rate and the initial physiological state. The biodiversity of the initiated communities was de-termined according to the planting from liquid nutrient media with polymers on the agar medium. Rank distributions of the studied indicators were abnormal, therefore, median and nonparametric dispersion analyzes were used, as well as a direct analysis of rank distributions. The bacterial community from coprolites acquires greater sustainability - the species composition becomes more leveled (the Berger-Parker index, showing the degree of dominance of the most abundant species, decreases after the passage) and diverse (the Shannon index becomes higher after passage). The hydrolytic bacterial complex is activated at passage, as the median value of the initial physiological state of the initiated communities increases. In the bacterial block, the proportion of fast-growing bacteria of r-strategists increases (on liquid media with polymers, the share of initiated hydrolytic associations increases with large values of the maximum specific growth rate).