AME 27:211-218 (2002)  -  doi:10.3354/ame027211

ABSTRACT: We developed a theory that uneven distribution of bacterial growth rates and different susceptibility to viral infection in bacterial community could result in higher estimates of virus production based on transmission electron microscopy (TEM) observation (VPTEM) compared to estimates obtained by neglecting uneven growth and different susceptibilities in the bacterial community. We tested this idea by classifying bacteria into 4 groups based on morphotypes (i.e. rods, cocci, curved shapes, and spirillae) and enumerating the frequency of visibly infected cells (FVIC) and the frequency of dividing cells (FDC; an indirect measure of the growth rates) in the 4 groups in the East Sea samples (n = 15). FVIC and FDC varied between different morphotypes and were highest in cocci. Further, FVIC and estimated growth rates of bacterial morphotypes were significantly correlated. The presence of a fast-growing bacterial group (apparently more susceptible to viral infection) in the bacterial community substantially increased (1.2 to 2.8-fold) the estimates of VPTEM in comparison to those obtained by using the mean growth rate of the bacterial community. Until now the differences between virus production measured by virus decay rates (VPD) and VPTEM have been thought to be explained by adsorption of viruses to particles, degradation of viruses due to enzymes and inactivation of viruses caused by sunlight. It seems that uneven growth and different susceptibility to viruses in the bacterial community might be another additional explanation for the discrepancy between VPD and VPTEM.

KEY WORDS: Virus production · Transmission electron microscopy · Uneven growth · Different susceptibility to viral infection