The Journal of Medical Microbiology, Vol 37, Issue 2 133-140, Copyright © 1992 by Society for General Microbiology
Effect of haemin limitation on the cytochrome complement and glucose metabolism of non-typable Haemophilus influenzae
T. O'Reilly, I. MacIver, R. K. Poole, D. F. Niven, P. G. Martin and M. R. Brown
Pharma Research, CIBA-GEIGY Limited, Basel, Switzerland.
Haemophilus influenzae grown to exponential phase or stationary phase in
medium with a low initial concentration of haemin (0.25 microgram/ml) was
virtually devoid of cytochromes. Compared with bacteria grown in the
presence of excess haemin (10 micrograms/ml), the haemin-limited organisms
failed to respire formate and succinate and, generally, the respiratory
rates with other substrates were reduced. However, growth rates were not
affected by the haemin supply. Haemin-limited growth was associated with a
reduced efficiency of glucose utilisation, in terms of glucose growth
yields, and affected the net levels of excreted organic acids. Haemin
limitation resulted in reduced acetate and increased succinate accumulation
in the culture medium and the novel presence of D-lactate. These results
indicate that, in contrast to the phenotype expressed in vitro during
conventional cultivation of H. influenzae, the haemin-limited phenotype,
which may be expressed in vivo, is characterised by a lack of cytochromes
and a shift towards a more anaerobic type of metabolism.
