Distribution of bacterial cell sizes and morphotypes in different seasons in the Sicily Channel Channel

Size is a key phenotypic trait of microbes that affects cell physiology and trophic interactions. In fact, size and shape of a cell affect the efficiency of nutrient uptake by determining the ratio of surface area to volume. Size-dependent mortality of marine prokaryotes contributes to the structuring of microbial assemblages since large cells are selectively grazed more than too small cells as well as too large cells cannot be ingested by protists. Moreover small cells may also be less susceptible to viral lysis. Finally, in combination with abundance quantification, the measurement of cell size and shape of prokaryotes of different populations is a prerequisite for obtaining a more detailed picture of biomass, production and carbon fluxes in microbial food webs. In spite of its importance, the biovolume of cells in microbial communities has not been extensively examined, although some data indicate that size varies among seasons and geographic locations due to variation in environmental conditions. Relatively few studies have so far dealt with prokaryotic size and shape in relation with environmental parameters and even a lower number has considered whether these parameters vary in relationship with different water bodies. In this context, this is the first study of prokaryotic size and shape distribution performed in the Sicily Channel with the aim of monitoring their phenotypic variability in different seasons. Seawater samples were collected during two oceanographic cruises in the frame of RITMARE Project, in Summer 2012 and Winter 2013. The variability of bacterial cell sizes and morphotypes was investigated - by using image analysis.