no 



Microbes and You 



to call one reaction or the other, it is important that young, 

 actively growing cultures be employed as source material. After 

 twenty-four hours of growth on laboratory media many gram 

 positive bacteria tend to lose their dye-holding capacity, and they 

 will yield a gram negative or a gram variable reaction. 



Table 8 



SOxME ORGANISMS THAT EXHIBIT A GRAM NEGATIVE 

 STAINING REACTION 



NAME OF ORGANISM 



FUNCTION, SOURCE OR HABITAT 



Aerobacter aerogenes 

 Azotohacter chroococcum 



Brucella abortus 



Escherichia coli 



Hemophilus pertussis 

 Neisseria intracellularis 

 Proteus vulgaris 



Salmonella typhosa 



Found in the soil, on plants and grains. 



Fixes atmospheric nitrogen non-symbiotically in 



the soil. 



The cause of contagious abortion in cattle and 



undulant fever in man. 



Inhabitant of the intestines of warm-blooded 



animals. 



The cause of whooping cough. 



The cause of epidemic meningitis. 



Found in certain infections and in putrefying 



material. 



The cause of typhoid fever. 



Table 9 



SOME ORGANISMS THAT EXHIBIT A GRAM POSITIVE 

 STAINING REACTION 



NAME OF ORGANISM 



FUNCTION, SOURCE OR HABITAT 



Bacillus anthracis 

 Bacillus cereus 

 Corynebacterium diphtheriae 

 Clostridium tetani 

 Diplococcus pneumoniae 

 Sarcina lutea 

 Streptococcus lactis 



The cause of anthrax. 



Found in soil and dust. 



The cause of diphtheria. 



The cause of tetanus, or lock-jaw. 



The cause of lobar pneumonia. 



Found in air, soil, water, and on skin surfaces. 



Found in milk and milk products. Plants may be 



the natural habitat. 



When attempting to identify a bacterial culture, the gram stain 

 is one of the first tests conducted on the organisms. If the stain 

 reveals a gram positive cell, the investigator can immediately 



