Mycobacterium phlei PN-bb colonies: a morphological characterisation by scanning and transmission electron microscopy.

Colonies of a non-acid-fast mutant of Mycobacterium phlei--termed "PN--bb"--were examined by scanning electron microscopy of gold-sputted whole colonies and by transmission electron microscopy of thin sections. Inspection of the colonies before and after preparation showed that the fixed colonies had retained their original appearance. Colonies are about 2-5 mm in height and width. They are made up of converging ridges forming a cone. These ridges consists of rounded bodies which are made up of clustered cells. The top of the cone consists of small, rugged, irregular structures. Thin sections show that the cells are arranged close together, without interconnections but with some electron-dense material between them. The colony is covered with a layer of unknown composition.