Effect of temperature on the growth and cell wall chemistry of a facultative thermophilic Bacillus

The morphology and cell wall composition of Bacillus coagulans, a facultative thermophile, were examined as a function of growth temperature. The morphology of the organism varied when it was grown at different temperatures; at 37 C the organism grew as individual cells which increased in length with increasing growth temperature. At 55 C it grew in long chains of cells. Cell wall prepared from cells grown at 37 C contained 44% teichoic acid by weight, whereas cells grown at 55 C contained 29% teichoic acid. Teichoic acid from these cells was a polymer of glycerol phosphate containing galactose and ester alanine. The ratio of ester alanine to phosphate was significantly higher in cell walls and teichoic acid from 37 C-grown cells compared with those from 55 C-grown cells. Other differences observed were that cells grown at 55 C contained a lower level of autolytic ability, produced cell walls which bound more Mg(2+), and contained less peptide cross-bridging in its peptidoglycan layer than cells grown at 37 C.

Isolation and characterization of cell wall-defective variants of Bacillus subtilis and Bacillus licheniformis

Quantitative mass conversion of intact bacterial cells of Bacillus subtilis and B. licheniformis to L-phase variants has been effected after lysozyme treatment. After subculture of the unstable L-phase variants for several months in the presence of methicillin, stable L-phase variants were obtained which grew in the absence of the antibiotic and were then unable to revert to the classical bacterial phase under conditions which gave rise to mass reversion of the protoplasts and unstable L-variants. These stable L-phase variants, which retained many of the physiological properties of the bacterium from which they were derived, were capable of growing exponentially and multiplying in liquid medium. Their morphology and apparent modes of reproduction were consistent with that described for other L-phase variants. The morphological events, as monitored by the electron microscope, of the reversion to the intact bacterial phase of an unstable L-phase variant of B. licheniformis are described.

Bacillus sp. ATCC 27380: a spore with extreme resistance to dry heat

An unusual mesophilic Bacillus sp. was isolated from heated soil, and a cleaned spore preparation showed extraordinary resistance to dry heat (D(125C) = 139 h) and relative sensitivity to moist heat (D(80C) = 61 min). Biochemical tests and morphology fit no described species.

Discriminatory ribosome rebinding of isolated regions of protein synthesis initiation from the ribonucleic acid of bacteriophage R17

To determine whether bacterial ribosomes recognize a distinguishing feature in the immediate vicinity of actual initiator codons or are directed to these sites through involvement of other portion(s) of the mRNA molecule, the interaction between ribosomes and defined (32)P-labeled initiator fragments from R17 RNA was studied. When incubated with mixtures of the three sites, ribosomes from Bacillus stearothermophilus (which initiate only the A protein on intact phage RNA) are able to select out the A fragment and discriminate against the coat and replicase initiator regions. By contrast, Escherichia coli ribosomes do not rebind that coat-protein region of R17 most efficiently, as they in the native RNA, but likewise prefer the A-protein initiator fragment. In both cases, ribosome binding of the isolated A site is comparable by several criteria to normal polypeptide-chain initiation on an intact R17 messenger RNA in vitro. E. coli ribosomal preference for the A site is confirmed in experiments with randomly fragmented R17 RNA, by both the initiation dipeptide and ribosome protection assay. Thus the A-protein ribosome-binding site of R17 RNA appears intrinsically to be a good initiator, while efficient recognition of the coat and replicase regions requires the participation of some portion of the remainder of the phage RNA molecule.