EFFECTS ON THE GROWTH OF MICROORGANISMS 981 



inhibited by the mercurials. It is clear that there is little or no selective ac- 

 tion on viruses growing in vivo, and the mercurials have not been found to 

 be effective virucidal or virustatic agents. Thus, although p-MB depresses 

 psittacosis virus formation in chick embryo cultures, it also inhibits tissue 

 growth, and it is quite possible that the effect on the virus is secondary to 

 that on the host cells (Burney and Golub, 1948). Corneal infections with 

 herpes virus are not benefited by application of p-MB, although the virus 

 is readily inactivated in vitro (Sery and Furgiuele, 1961), and mercurials 

 are not effective in preventing or treating plant virus infections. Kaplan 

 (1959) concluded that mercurials react with SH groups on the surface of the 

 virus and thus prevent attachment to the host cell. Certainly the hemagglu- 

 tinating activity and the adsorption onto erythrocytes are depressed along 

 with the infectivity (Choppin and Philipson, 1961). Adsorption of entero- 

 viruses onto renal cells may also be reduced, but p-MB does not prevent 

 adsorption of influenza virus onto the chorioallantoic membrane. Further- 

 more, p-MB does not prevent infection of E. coli by phage but inhibits the 

 proliferation. Allison (1962) holds that the mercurials do not affect the 

 primary attachment of the virus to the host cell, but may prevent the un- 

 coating of the virus, an event which precedes multiplication. The studies 

 of Shug et al. (1960) on T2 phage show that here the inhibition by p-MB is 

 exerted early in the development, the maximal inhibition being 10-20 min 

 after infection. This excludes the energy-yielding host metabolism as a pri- 

 mary site of action, since the energy requirements are greater after 25 min 

 when the phage is being synthesized and assembled. They conclude that 

 the site of attack is a protein concerned with the initial phases of replica- 

 tion and possibly involved in the assembly of the components into an in- 

 tact phage. It would not be surprising if the site of mercurial action, or 

 the phase disturbed, is different for the various phages and viruses. 



Protozoa 



Ciliates are immobilized and killed by the mercurials but the results re- 

 ported are quantitatively discrepant. Nuhaus (1910) found that 0.15 milf 

 Hg++ paralyzes paramecia in 50 min and kills them in 70 min, but Wood- 

 ruff and Bunzel (1910) stated that 0.175 mM Hg++ stops all motion within 

 2 sec. Even greater sensitivity was reported by Gause (1933), as indicated 

 in the accompanying tabulation. It should be noted that actually death 



Hg++ (milf) Duration of life (sec) 



