- Volume 20, Issue 3, 1959

SUMMARY: The flagellation and motility of Salmonella typhimurium were unaffected by proteolytic enzymes; but when washed stationary-phase bacteria were briefly exposed to acid (e.g. pH 2·6 for 30 sec. at 43°) the proportion of motile, and of flagellated, bacteria was decreased from more than 50 % to less than 1 %, with little or no decrease in viable count. When 5. typhimurium or Vibrio metchnikom grown on stiff agar were rubbed for several minutes on the agar, the proportion of motile and of flagellated bacteria was decreased from c. 90 % (found in control bacteria, soaked off without rubbing) to c. 1 %, without decrease in viable count. High-speed stirring in a blendor also deflagellated and destroyed the motility of 5. typhimurium in suspension, without killing the bacteria or retarding their growth. Blendor treatment sufficient to deflagellate 5. typhimurium had no effect on the movements of certain non-flagellated motile organisms (Leptospira canicola, Treponema pallidum and T. duttoni), except when it caused gross morphological changes, attributed to cell damage. When log-phase broth cultures of 5. typhimurium deflagellated in the blendor were incubated, bacteria with flagella (at first all short) and motile bacteria soon reappeared. At first many bacteria rotated; this suggests that flagella shorter than c. 0·3 μ cause rotational, but not translational, motility. The rate of increase of mean summed flagellar length/bacterium was compatible with the hypothesis that flagella are not (spontaneously) shed in broth cultures of 5. typhimurium and that the rate of growth of flagella is unaffected by deflagellation. Up to one generation time after deflagellation the mean number of flagella/bacterium was, however, less than before deflagellation. It is inferred that in a log-phase culture about half the flagella present at any one moment are ‘fully-grown’, incapable of being regenerated when broken off. All the results obtained are compatible with the hypothesis that the motility of flagellated bacteria is due to active movement of their flagella.

During work on the genetics of motility and flagellation in salmonella a nonlethal method of removing flagella from bacteria was needed. No satisfactory way of stripping selected individual bacteria of their flagella has been found, but it appeared that whole cultures might be deflagellated, without killing the bacteria, by several different methods. Such methods should provide a test of the hypothesis that the motility of flagellated bacteria results only from the active movement of their flagella, for total removal of the flagella would then necessarily result in loss of motility; whereas if normal motility in salmonella, etc., results from alterations of the shape of the bacterial body (Pijper, 1948, 1957), a treatment which removed all flagella might still leave motility unaffected. The effect of the application of similar treatment to motile bacteria which do not possess flagella (Leptospira, etc.) was also investigated, as a partial ‘control’ on the effects, other than deflagellation, of one of the treatments used. The manner and rate of the reappearance of flagellar

Summary: Solanine toxicity was assessed by its effect on the viability of spores of Fusarium caeruleum. Factors which were found to influence toxicity included solanine concentration, period of exposure, hydrogen-ion concentration, spore density, the Na ion/Ca ion ratio and the previous history of the spores. The toxicity of some related compounds was determined, and the toxicity of solanine to some other micro-organisms. The effect of solanine on the growth of F. caeruleum in culture was investigated. The nature of the toxic action of solanine on fungus spores and the similarity of spore toxicity to haemolytic activity are discussed. It is concluded that the presence of solanine is unlikely to be an important factor in preventing fungal infection of those tissues in which it is found.

Summary: With a strain of Fusiformis nigrescens as test organism, the potencies of compounds of the vitamin K group were estimated, and the results compared with those from animal assay techniques. The compounds showed in the main the same relative activity for the micro-organism as for higher animals, with two exceptions: 1 : 4-naphthoquinone was highly active for F. nigrescens but is inactive for animals; phthiocol, which is active for animals, inhibited the response of F. nigrescens to menaphthone, i.e. phthiocol acted as an anti-vitamin K for the micro-organism. Most of the compounds tested were toxic in the range 1–5 µg./ml.; vitamins K1, K2 and a water soluble form of menaphthone (menaphthone bisulphite) were relatively less toxic.

Summary: The early events in the infection of tobacco and Nicotiana glutinosa by tobacco mosaic virus occur sooner when the inoculum is the nucleic acid of the virus than the whole virus. In plants at 28° newly formed virus becomes detectable between 6 and 8 hr. after inoculation with the nucleic acid and after 8–10 hr. with whole virus. Although the latent period is lengthened by lowering temperature, the difference between the lengths of the latent periods given by the two inocula is little changed. Infective centres initiated by nucleic acid also become resistant to hot- water treatment (a 30 sec. dip in water at 50°) about 2–4 hr. sooner than do those initiated by whole virus.

Exposure of inoculated plants to 37° decreases the number of lesions produced by the nucleic acid much more than by whole virus; resistance to this treatment develops from 30 to 120 min. after inoculation with the nucleic acid, depending on the temperature at which the plants are kept.