Frequency, size and distribution of bacteriophages in different marine bacterial morphotypes

Abstract

The frequencies of cells containing mature phages, the burst sizes, the phage head sizes and the distribution of phages inside cells of different bacterial morphotypes were investigated in the northern Adriatic Sea. Coccoid bacteria more frequently (2.5%) contained mature phages than rodshaped bacteria (1.2%) and spirillae (1.4 %). Including an estimation of non-v~sible infection we found that up to 27 % of rods were infected with viruses, up to 79% of cocci and up to 100% of spirillae. The highest overall infection frequency of the entire bacterial community was 30 %. The percentage of rods with mature phages was significantly correlated to increasing rod densities. It is suggested that a threshold density of about 2 X 10' rods ml-' exists that is necessary for infection with phages. No threshold densities could be determined for cocci and spirillae. Burst sizes varied strongly between different host morphotypes. The burst sizes of rods increased significantly with the frequency of rods containing mature phages, probably as a result of superinfection of bacteria with phages. The volume of the host cells seemed to influence the number of phages produced per cell. Most of the phages within rods and all phages within spirillae were smaller than 60 nm, whereas the majority of phages within cocci were larger than 60 nm. Analyses of the distribution of phages inside the cells showed that phages were frequently concentrated in 2 defined areas at the 2 opposite ends of both rods and spirillae. Our results from an in situ study suggest that the production of bacteriophages is strongly influenced by the structure of the bacterial community, i.e. by the relative abundances of the various morphotypes.

Seasonal Variation of Virioplankton in a Eutrophic Shallow Lake

“…Grids were examined for visibly infected cells under TEM. The viral burst size was estimated for each sample by counting the number of viral particles in a minimum of 15 visibly infected bacteria as described previously (Weinbauer & Peduzzi, 1994). A minimum of five phages were observed in a visibly infected cell.…”

Global morphological analysis of marine viruses shows minimal regional variation and dominance of non-tailed viruses

“…Viral morphology is central to modern viral taxonomy (King et al, 2012) and commonly correlates with whole-genome-derived taxonomy (Rohwer and Edwards, 2002) and aspects of their biology (reviewed by Ackermann, 2001). Thus, morphological metrics have applications ranging from medical diagnostics (Doane, 1980) to environmental virology (for example, Bratbak et al, 1990;Weinbauer and Peduzzi, 1994). In aquatic environments, morphological metrics documented spatiotemporal changes in viral assemblages, revealing aquatic viruses as dynamic and varied across large environmental gradients Auguet et al, 2009;Brum and Steward, 2010;Bettarel et al, 2011a, b).…”

Distribution of marine viruses in the Central and South Adriatic Sea

“…In the Adriatic Sea, the studies of marine viral abundances were carried out mostly in the northern Adriatic Sea (Weinbauer et al, 1993;Weinbauer & Peduzzi, 1994;Weinbauer et al, 1995;Luna et al, 2002;Corinaldesi et al, 2003;Stopar et al, 2003;Bongiorni et al, 2005;Karuza et al, 2010Karuza et al, , 2012, whereas data from the eastern coastal Adriatic Sea are scarce. In a comprehensive study, Corinaldesi et al (2003) determined the viral abundance throughout the Adriatic Sea, but did not collect data from Croatian territorial waters.…”