196 Microbes and You 



thev use the products getting the greatest attention in print and 

 on the air. To protect a gulhble pubHc from false and misleading 

 advertising, State and Federal agencies have been established to 

 deal with problems arising from the sale of foods, drugs, and 

 cosmetics. 



By adding chemicals to the environment of microbes, it is 

 possible to demonstrate a phenomenon called chemotaxis— the 

 response of microorganisms to chemicals. If organisms are at- 

 tracted to chemicals, this is positive chemotaxis, and the repelling 

 action of other chemicals results in negative chemotaxis. Con- 

 trary to earlier beliefs, however, there is no relationship between 

 this migration of organisms and the killing action of the specific 

 chemical. Some agents will lure bacteria to their destruction while 

 other lethal compounds will repel organisms. A completely satis- 

 factory explanation of chemotaxis is still not available. 



Many tenns employed in discussing chemical effects on bacteria 

 are used with different meanings by various individuals. It seems 

 worth while at this point to define a few words commonly em- 

 ployed in such discussions. 



1. Antiseptic: A substance or agency that prevents sepsis, putre- 

 faction, or decay. It is usually employed to control infectious 

 agents on epithelial surfaces, mucous membranes, and super- 

 ficial wounds. 



2. Germicide: Anything that destroys germs (microscopic organ- 

 isms), particularly pathogenic organisms. 



3. Bactericide: Anything that destroys bacteria. 



4. Bacteriostat: An a2;ent which inhibits bacteria but does not 

 kill them, at least not for some time. 



5. Disinfectant: An agent or process that frees from infectious or- 

 ganisms. It is generallv thought of in terms of destroying or- 

 ganisms apart from a living animal. The word is generally used 

 to describe the destruction of bacteria which have already 

 initiated an infection, in contrast to an antiseptic which prevents 

 pathogenic organisms from gaining a foothold. Pasteurization, 

 however, may be employed to disinfect milk. 



