Table 3. Effects of genetic modification the C-terminal needle domain.

Phage sourcea	Lysate titerb	Virion infectivityc
UB-1790 Parent P22 phaged	1.7×1010	1.0
UB-2083 HS1-1 hybrid needle phage	7.5×109	1.1
UB-1918 Sf6-3 hybrid needle phage	6.2×109	2.1
UB-1919 Glu146Asp	5.5×109	0.8
UB-1920 Glu146Ala	5.2×109	1.7
UB-1925 Lys200Ala	1.4×109	2.0
UB-1926 Lys200Glu	2.6×109	1.4
UB-1921 Ser248Thr	6.3×109	2.0
UB-1922 Ser248Ala	3.8×109	2.1
UB-1924 Asp250Ala	2.1×109	2.9
UB-1927 Glu146Ala/Asp250Ala	1.8×1010	1.0
UB-1928 Lys200Ala/Asp250Ala	1.4×109	1.8
UB-1929 Glu146Ala/Lys200Ala	2.9×109	1.3
UB-1941 Foldon	8.3×109	0.13

^a Salmonella lysogens are listed that were induced to prepare stocks of the phages in the table; the amino acid changes in the L-glutamate binding site of the needle are shown after the Sf6-hybrid needle phage strain names (UB-1919 to 1929).

^bLysogens were induced with mitomycin C and titered on Salmonella strain UB-0002; average results from several replicates are shown.

^cPhage particles were purified through CsCl step gradients [68], and phage titers were determined on Salmonella strain UB-0002. Relative PFU/particle ratios were calculated by normalization to UB-1790 titer (PFU) and to the intensity of quantified coat protein bands in SDS electrophoresis gels and/or OD₂₈₀ (particles). Several replicates were performed for each phage with similar results, and the average value is shown.

^dThe prophages all have the following genetic background: P22 26::Sf6-3, sieA^–Δ1, 15^–ΔSC302::Kan^R, 13^–amH101 (see table 2).