Biochemical and morphological changes in Escherichia coli irradiated by coherent and non-coherent 632.8 nm light.

Irradiation of Escherichia coli cells with either coherent or non-coherent 632.8 nm light (4 J cm-2) causes a transient acceleration of cell proliferation, which is maximal about 60 min after the end of the phototreatment. The stimulatory effect is dose dependent and is especially evident in the case of defective E. coli strains which are in the logarithmic phase of growth, while it becomes less important when cells are exposed to non-coherent 600-700 nm light. Stimulated cells exhibit biochemical and morphological changes, such as an intensified synthesis of cytoplasmic membrane proteins, increased cell volume and ribosomal content, which are suggestive of an enhanced cell metabolism.