Bacterial abundance and diversity in ocean waters varies at the millimeter scale, and organic-rich particles represent "hot spots" for microbial activity. Remarkably, the bacteria found attached to particles are genetically distinct from those in the surrounding water. Bacteria that colonize particles employ species-specific enzymes that breakdown the organic content at different rates. Since sinking particles in the ocean represent a major mechanism influencing global carbon flux, bacterial metabolic activity on marine particles is an important factor in biogeochemical cycling. However, little is known regarding the variables that regulate microbial diversity on and around marine particles. This study will investigate mechanisms controlling micro-scale diversity and interactions among marine microorganisms colonizing particles. A specific focus will be microbial competition, and the possibility that pelagic bacterial population structures are influenced by the production of antibiotics. Experiments will be conducted to quantify the effects of bacterial antagonistic interactions at the molecular, single-bacteria cell, consortia, and community levels. The colonization of model particles by microbial natural assemblages will be measured in response to fluorescence-tagged antagonistic strains. Growth and respiration of sensitive strains in close proximity to antagonistic bacteria will be measured to quantify interactions at the single-cell level. Molecules produced by antagonistic bacteria will be identified and tested for their effects on particle colonization by single strains and natural consortia of bacteria.
This is the first, in depth investigation to probe cell-cell antagonistic interactions as a micro-scale factor involved in structuring marine microbial communities. Knowledge of microbial diversity on suspended particles will be advanced, and the interactions and specific adaptations involved in surface colonization will be better understood. This endeavor will further fuse connections between marine bacterial chemical ecology, microbial diversity, and biogeochemical cycling. Undergraduate and graduate students will be cross-trained in chemical ecology and molecular microbial ecology, and future teachers will learn molecular and microbiological techniques and concepts during one-year internships.
