Josephine Johnston

The soil microbiome is a diverse environment that is heterogeneous, both physically and chemically. An important microbial trait in a spatially structured environment like soil is a microbe’s morphological strategy, filamentous or non-filamentous. Within the soil matrix, necromass (dead microbial material) represents a significant portion of all soil organic matter, which is the biggest terrestrial carbon pool on earth. The aim of this study was to disentangle the chemical and physical microbial traits that allow microbes to decompose necromass by identifying the degree to which morphological traits across and within domains explain decomposition capacities. Eight fungal species and eight bacterial species from the Kennedy lab culture collection were inoculated into soil microcosms as monocultures. A bag of necromass was added to each jar as a carbon source; the mass of the bag was measured before and after incubation to measure mass loss. Respiration was quantified by measuring carbon dioxide production over time. As hypothesized, filamentous fungi had a greater respiration rate than other organisms. One filamentous bacteria, Streptomyces sp. 30, had a greater respiration rate and mass loss than other bacteria and non-filamentous fungi. There was little difference in respiration rate and mass loss between other bacterial species and non-filamentous fungi. This study suggests that morphology influences an organism's ability to decompose necromass to a greater degree than previously assumed.