ABSTRACT

The tubercle bacilli of the genus Mycobacterium are thin, straight rods measuring approximately 0.4m3m. They are characterized by their acid-fast staining, which is contingent on the fact that, once stained by basic dyes, they cannot be decolorized by alcohol. The mycobacteria are obligatory aerobes. In contrast to most bacteria, their replicating cycle is of the order of 17 to 24 hours. The tubercle bacilli are relatively resistant to desiccation and may survive for long periods in dry sputum.