Phage tf-1: A Filamentous Bacteriophage Specific for Bacteria Harbouring the IncT Plasmid pIN25

Abstract

Phage tf-1 is a filamentous phage which is about 800 nm in length, 10 nm in width and has slightly tapered ends. The phage was isolated from sewage and formed plaques or propagated only on Escherichia coli, Salmonella typhimurium and Klebsiella oxytoca strains harbouring the IncT plasmid pIN25 at 30 degrees C. It adsorbed in large numbers to pIN25-encoded long thick flexible conjugative pili formed at 30 degrees C and also to the short form of these pili synthesized at 37 degrees C. The reason for the failure to form plaques at 37 degrees C is not known. The adsorption site is a short length of the pilus shaft extending 100-200 nm back from the distal tip. Efficient phage tf-1 adsorption to the same site was found for pili determined by other IncT plasmids in spite of the fact that phage tf-1 did not plate or propagate on strains harbouring them. However, areas of specific partial clearing on lawns of these plasmid-containing bacteria were produced by phage in high concentrations. Lack of plaque-formation could be due to inefficient intracellular assembly coupled to avid adsorption of any liberated phage to pili. The phage differs from all but one other filamentous phage by being sensitive to diethyl ether.

Escherichia coli tolQ Mutants Are Resistant to Filamentous Bacteriophages That Adsorb to the Tips, not the Shafts, of Conjugative Pili

“…Electron microscopy showed that it attached along the pilus shaft ( Fig. 1) and was not specific for the tip or any area close to it, as was the case for tf-1 (Coetzee et al, 1987). This explained why the to@ mutation did not affect it.…”

“…Phage X has a very wide plasmid specificity range, but it is not known whether this is connected with its insensitivity to the to@ effect. Filamentous phage X-2 (IncX-specific), whose receptor was not identifiable due to poor adsorption (Coetzee et al, 1988), was also inhibited by to@; because of this, it seems very likely that it attaches to the tips of X pili. The inhibition of phage PR64 infection by to@ is noteworthy.…”

Bacteriophage X-2: a Filamentous Phage Lysing IncX-Plasmid-harbouring Bacterial Strains

“…Strain JE2571, carrying the IncFl plasmid R386 (Dennison, 1972) was the indicator for phage fd (see below). Other plasmids belonging to Inc groups C (Sirgel et al, 1981), D (Coetzee et al, 1985a), HI and HI1 (Coetzee et al, 19853), J (Bradley et al, 1982a), S (Coetzee et al, 1986) and T (Bradley et al, 1981 b ;Coetzee et al, 1987) were also used in phage host-range experiments. Constitutive production of conjugative pili by the above plasmids was assessed by the ability of corresponding plasmid-specific phages, described in the same references, to form plaques on lawns of the plasmid-bearing organisms.…”

“…Constitutive production of conjugative pili by the above plasmids was assessed by the ability of corresponding plasmid-specific phages, described in the same references, to form plaques on lawns of the plasmid-bearing organisms. Filamentous phage X (Bradley et al, 1981 a) the X-like phages IKe (Khatoon et al, 1972) and 12-2 (Coetzee et al, 1982;, phages PR64FS (Coetzee et al, 1980), fd (Marvin & Hoffmann-Berling, 1963), SF (Coetzee et al, 1986) and tf-1 (Coetzee et al, 1987) were compared serologically with phage X-2 (see Results). The RNA-containing phage C-1 (Sirgel et al, 1981) and filamentous phages X, IKe, PR64FS and fd were used as controls in organic solvent and RNAase susceptibility tests.…”

“…Apart from its specificity for IncX-harbouring bacteria, it differed from other filamentous phages in other respects: phage X has a frankly curly appearance (Bradley et al, 198 1 a ; compared to filamentous phages like f 1 (Caro & Schnos, 1966), IKe (Khatoon et af., 1972;, PR6FS (Bradley, 1983), C-2 (Bradley et al, 1982a), SF (Coetzee et al, 1986) and tf-1 (Coetzee et al, 1987). Secondly the phage had a very broad host range in that it plated on bacterial strains harbouring plasmids of Inc groups 12, M, N, P-1, U and W. This host range partially overlaps that of phages IKe and It-2 (Coetzee et al, 1982) and these phages are here named X-like for that reason (see Bradley et al, 1983).…”