<P> Many Mycobacterium species adapt readily to growth on very simple substrates, using ammonia or amino acids as nitrogen sources and glycerol as a carbon source in the presence of mineral salts . Optimum growth temperatures vary widely according to the species and range from 25 ° C to over 50 ° C . </P> <P> Most Mycobacterium species, including most clinically relevant species, can be cultured in blood agar . However, some species grow very slowly due to extremely long reproductive cycles--M. leprae, may take more than 20 days to proceed through one division cycle (for comparison, some E. coli strains take only 20 minutes), making laboratory culture a slow process . In addition, the availability of genetic manipulation techniques still lags far behind that of other bacterial species . </P> <P> A natural division occurs between slowly--and rapidly--growing species . Mycobacteria that form colonies clearly visible to the naked eye within seven days on subculture are termed rapid growers, while those requiring longer periods are termed slow growers . Mycobacteria cells are straight or slightly curved rods between 0.2 and 0.6 μm wide and between 1.0 and 10 μm long . </P> <P> Some mycobacteria produce carotenoid pigments without light . Others require photoactivation for pigment production . </P>

Which of the following is true regarding species of mycobacterium