L Variation in Mycobacteria1,2

Abstract

The bacterial forms known as L variants have been cultured from many genera, but none have been reported as occurring in mycobacteria. This paper summarizes a four-year investigation of Mycobacterium species, testing their ability to produce L forms under varied conditions. The subject of L forms in mycobacteria has especial interest because some investigators now believe the atypical structures observed in vivo since 1883 (1) may be stages of the L cycle. Therefore, it is important that L growth be studied if the atypical form is to be cultured from infected tissue and its reversion to the distinctive acid-fast rod facilitated. Interest in virulence of L variants has been raised by Rubio-Huertos (2), who found that Clostridium tetani produces an L variant more toxic than the bacillary form. The demonstration of L variation in mycobacteria brings to a conclusion the extensive controversy concerning filtrability of tubercle bacilli (3-6). It is recognized that L variants have minute particles capable of initiating growth. Thus, 'without resort to filters, L colonies demonstrated filtrability.