SIGNIFICANCE OF LYSOGENY IN THE MARINE-ENVIRONMENT - STUDIES WITH ISOLATES AND A MODEL OF LYSOGENIC PHAGE PRODUCTION

The importance of lysogeny in marine microbial populations is just beg inning to be understood. To determine the abundance of lysogens in bac terial populations, we studied the occurrence of lysogenic bacteria am ong bacterial isolates from a variety of marine environments. More tha n 116 bacteria isolated on artificial seawater nutrient agar plates we re tested for the presence of inducible prophage by mitomycin C and UV radiation. Induction was determined as a decrease in culture absorban ce at 600 nm, after treatment with inducing agents. Samples in which o ptical density decreased or remained the same after induction were fur ther examined by transmission electron microscopy, for the presence of virus-like particles. More than 40% of the bacterial isolates contain ed inducible prophage, as determined by mitomycin C induction. A highe r percentage of lysogenic bacteria was found in isolates from oligotro phic environments, compared to coastal or estuarine environments. Thes e studies suggest that lysogenic bacteria are important components in marine microbial populations. However, a mathematical model based on v iral and bacterial abundance and production rates suggests that, under normal conditions, lysogenic viral production contributes less than 0 .02% of total viral production. Therefore, lysogens in the marine envi ronment may serve as a source of viruses and only contribute significa ntly to viral production during natural induction events.