Cultivation requirements for Treponema pallidum, Mycobacterium leprae and other microbial and mammalian microaerophilic cells

Factors influencing the in vitro growth of Mycobacterium leprae: effect of oxygen

In our efforts to evaluate factors responsible for in vitro growth of Mycobacterium leprae in DH medium and also to improve the system, effects of oxygen tension on in vitro growth of M. leprae were determined. This was achieved by varying the ratio between DH medium and free air space above the medium in the culture tubes. Growth-competent M. phlei (ATCC 11758) could tolerate all the oxygen it can get in the medium. On the other hand, M. leprae seemed to be of microaerophilic nature. In vivo-grown M. leprae cells were more sensitive than their counterparts that were adapted to in vitro environment. In vivo-grown cells grew better when 70% of the space in culture tube was occupied by DH medium. These in vitro-adapted cells gave optimum growth in subcultures when the air spaces in the culture tubes were 40-50%. The role of oxygen tensions in the development of lesions in leprosy patients and armadillos has been discussed.

Redox potential and survival of virulent Treponema pallidum under microaerophilic conditions

A strongly reduced culture medium, capable of maintaining the virulence of Treponema pallidum (Nichols) for several days, was exposed to an atmosphere of 3% oxygen in nitrogen for 2-3 days before inoculation with T pallidum. By using various volumes of medium in uniform tubes a range of redox potentials (Ecal) from -94 mV to -325 mV was produced depending on the surface area-to-volume ratios of the medium. The anaerobic medium had an Ecal value of -387 mV. The medium was inoculated with T pallidum and incubated in an atmosphere of 3% oxygen. The survival of treponemes at different redox potentials was monitored by observing the retention of motility and by measuring the latent period of infection after inoculation of the cultures into the shaved backs of rabbits. Under these conditions T pallidum survived longest at low (electronegative) redox potential. An inverse linear relationship was observed between the redox potential of the culture medium and the survival of T pallidum, as measured by the time required for a 90% reduction of virulent organisms. No optimum redox potential was detected, the most electronegative medium (-325 mV, Ecal) giving the best survival.

Pain: evolutionary background and primary stimulus

The evolution of aerobic organisms required the development of oxygen sensors so the organism could avoid anoxic environments. In man these oxygen sensors are known as pain receptors. The skin pain receptor includes the epidermis and the dermal papilla with its capillary and terminal nerve. A pain stimulus such as a pin prick occludes blood flow into the papilla. The epidermal cells consume enough residual oxygen to produce a fall in oxygen tension at the nerve ending sufficient to cause the nerve to fire. The maximum time required for the oxygen drop is 0.04 seconds.