Chan, A.M., I. Kacsmarska and C.A. Suttle (submitted). Isolation and characterization of a species specific bacterial pathogen which lyses the marine diatom Navicula pulchripora. Abstracts of the American Society of Limnology and Oceanography, Santa Fe, NM, February 1997.

A lytic bacterium which infects a marine pennate diatom was isolated from the coastal waters of Texas. Analysis of 16S rDNA gene sequences show that it is closely related to the Cytophaga-Flavobacter group of bacteria. The pathogen is 0.1 mm filterable and can be propagated indefinitely by transferring a small inoculum from an infected culture into an uninfected culture. The pathogen can also be cultured on organically-enriched media. Introduction of the pathogen to healthy cultures of Navicula pulchripora results in lysis of the diatoms within a few days. The bacterium was unable to infect 9 other pennate and centric diatoms that were tested. Observation of the infection process by transmission electron microscopy revealed membrane-bound ellipsoid and spherical bodies in the cytoplasm of infected cells. These results suggest that bacterial pathogens can be important in regulating diatom populations.