. 2018 Mar 7;10(3):115. doi: 10.3390/v10030115

Table 2.

Influence of C-terminal cII amino acids and host properties on cII complementation, toxicity and plasmid loss.

Host [Plasmid] ^a	Intensity of CII-Activated CI₄₃₄ Repression at 37–39 °C ^b	λimm434 cII⁻ Plaque Formation at 37–39 °C ^c	Cell Viability, (±SE) and [% Plasmid Loss] Per Growth Temp. of Transformants ^e
Host [Plasmid] ^a	Intensity of CII-Activated CI₄₃₄ Repression at 37–39 °C ^b	λimm434 cII⁻ Plaque Formation at 37–39 °C ^c	39 °C	42 °C
594 [cII] = [cII_1–97]	H (high)	−	0.03 (0.001) [0]	<0.001 (0.0001) [100]
594 [cII-oop-pO94]	0 (none)	+ ^d	0.59 (0.03) [0]	0.08 (0.03) [0]
594 [cII_1–92]	H	−	0.73 (0.01) [0]	0.005 (0.001) [100]
594 [cII_1–87]	H	−	0.76 (0.02) [0]	0.08 (0.03) [0]
594 [cII_1–77]	0	+ ^d	0.74 (0.10) [0]	0.32 (0.10) [0]
594 [cII-3638](38,642: A-G, M-V)	H	−	0.62 (0.10) [0]	0.002 (0.0004) [89]
594 [cII-3639](38,634: A-G, Q-R)	H	−	0.76 (0.02) [0]	<0.001 (<0.0001) [19]
594 [cII-3638–3639]	H	−	0.65 (0.04) [0]	<0.001 (<0.0001) [6]
594 hflA::kan [cII]	S (slight)	+	0.89 (0.01) [0]	0.008 (<0.0001) [100]
594 hflA::kan [cII_1–92]	S	+	0.69 (0.01) [0]	<0.001 (<0.0001) [100]
594 hflA::kan [cII_1–87]	S	+	0.85 (0.02) [0]	0.24 (<0.0001) [0]
594 hflA::kan [cII_1–77]	0	+ ^d	0.86 (0.10) [0]	0.58 (0.01) [0]
594 hflA::kan [cII-oop-pO94]	0	+ ^d	0.63 (<0.0001) [0]	0.001 (0.0002) [100]
594 pcnB::kan [cII]	0	+ ^d	<0.001 (0.01) [67]	<0.001 (0.0001) [100]
594 pcnB::kan [cII-oop-pO94]	0	+ ^d	0.46 (0.01) [64]	<0.001 (0.0003) [89]

^a All strains were made by transformation of an Amp^R plasmid into strain 594, or into 594 cells that had been transduced with hflA::kan or pcnB::kan markers. All CII protein deletions were from the COOH-terminal end, where the WT CII is represented as cII_1–97. ^b Intensity of CII-activated CI repression depends upon CII expression from the plasmid stimulating pE-cI⁴³⁴ transcription from an infecting λimm434cII⁻ phage genome. “H” indicates a high level of CII complementation of the cII-defective infecting phage by the plasmid-encoded cII allele. The high level of CI⁴³⁴ expression from the phage genome represses lytic development, preventing the formation of individual plaques and phage lysis spots on overlay plates incubated at 37 and 39 °C. “0” indicates that no CII complementation was detected and the infecting phage plated, forming clear plaques, at an equivalent efficiency to that observed on overlaid 594 host cells without a plasmid. “S” indicates slight CII complementation, insufficient to block lytic phage growth and plaque formation and yielding weakly turbid plaques, suggesting the CII activity was not sufficient to drive establishment pE-cI⁴³⁴ transcription and CI⁴³⁴ repressor synthesis to a level that could prevent lytic growth of the infecting λimm434cII^- phages. ^c Plaquing designations: “−” indicates that no individual plaques were observed in spots of 16 or 160 pfu and faint or no lysis was evident when 16,000 pfu were spotted. “+” indicates cell lysis when 16,000 pfu were spotted and individual pfu formation in each of the spot areas with applied 160 or 16 pfu. ^d Individual plaques were clear. ^e Measurements for plasmid loss: a minimum of 36 cfu per assay plate per plating temperature were screened, in triplicate. The assay was also conducted in parallel (for every experiment shown herein) at 30 °C, where there is no cII expression due to the fully active λ CI Ts857 repressor and at 37 °C; and for each assay, the viability was 1.0 with no plasmid loss.