The Effect of Non-Lethal Deflagellation on Bacterial Motility and Observations on Flagellar Regeneration

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