Cytological observations onBact. coli, Proteus vulgarisand various aerobic spore-forming bacteria with special reference to the nuclear structures

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Abstract
1. The basic observations of Piekarski (1937–40) and F. Neumann (1941) on Feulgen-positive, chromatinic structures, going through a regular cycle of division, in the cells ofBact. coliandProteus vulgarisare confirmed and the view that these structures are nuclear in nature is accepted.2. The chromatinic structures in bacteria from old cultures, although usually distinguishable from the cytoplasm, are too small to be resolved accurately. After transfer to a fresh nutrient medium the chromatinic structures increase in size and give rise to short, often dumbbell shaped, rods (chromosomes) which multiply by splitting lengthwise in a plane more or less parallel with the short axes of the bacterium.3. The chromatinic structures ofBacl. coliand ofProteus vulgarisare essentially the same as those previously described in myxobacteria and actinomycetes (Badian, 1930, 1933, 1936) and in various well-known aerobic spore-forming bacteria (Badian, 1933, 1935; Robinow, 1942).4. A single cell ofBact. coliorProteus vulgariscontains one chromatinic body or one or two pairs of these, representing primary and secondary division products.5. Few bacteria from young cultures are single cells. When fixed through the agar with Bouin's mixture and stained briefly with Giemsa's solution, bacteria from young growing cultures ofBact. coli, Proteus vulgaris, B. mesentericusandB. megatheriumassume a banded appearance indicating that each bacterium consists of two, three or four separate cells.6. A plasmolysing treatment has been applied toB. megatheriumwhich provides direct proof of the composite structure of this bacillus by inducing its component protoplasts to shrink away independently from the outer supporting cell wall.I wish sincerely to thank Dr H. B. Fell for the hospitality offered to me at the Strangeways Laboratory, for her sustained interest in this investigation and for her help in preparing the manuscript for the press. I have also pleasure in admitting my indebtedness to Prof. E. G. Pringsheim for much helpful criticism and advice in matters relating to the bacterial cell wall.