This study aims at assessing the influence of Pseudomonas fluorescence cell morphology on the effectiveness and production of the lytic bacteriophage I center dot IBB-PF7A. P. fluorescens were cultured as rods or as elongated cells by varying the temperature and rotary agitation conditions. Cells presented rod shape when grown at temperatures up to 25A degrees C and also at 30A degrees C under static conditions, and elongated morphology only at 30A degrees C when cultures were grown under agitation. Elongated cells were 0.4 up to 27.9 mu m longer than rod cells. Rod-shaped hosts were best infected by phages at 25A degrees C which resulted in an 82% cell density reduction. Phage infection of elongated cells was successful, and the cell density reductions achieved was statistically similar (P > 0.05) to those obtained at the optimum growth temperature of P. fluorescens. Phage burst size varied with the cell growth conditions and was approximately 58 and 153 PFU per infected rod and elongated cells, grown at 160 rpm, at 25A degrees C (the optimal temperature) and 30A degrees C, respectively. Phage adsorption was faster to elongated cells, most likely due to the longer length of the host. The surface composition of rod and elongated cells is similar in terms of outer membrane proteins and lipopolysaccharide profiles. The results of this study suggest that the change of rod cells to an elongated morphology does not prevent cells from being attacked by phages and also does not impair the phage infection.