Abnormal cellular morphology associated with a vitamin B6 deficiency in Lactobacillus arabinosus.

tions and advantages of this method have been reported (Barber, J. MIilk & Food Technol., 12, 257-266, 1949), and it is well to point out here the obvious economy in incubator space, agar medium, time, and productivity. Usually, 4 to 5 ml of agar are used per tube. Samples (1 ml or some fraction thereof) aire added to the sterile, melted, and tempered agar; the tubes are agitated gently, slanted in racks, and incubated in an inverted position. Accurate "plate" counts can be made wvitl comparative ease using a Quebec Colony Counter. To facilitate counting, an adapter has been developed for the counter which has the effect of blocking out unnecessary glare and providing excellent light contrast. A piece of V4" wood (roughly rectangular-7 by 412 "), notched to fit snugly on the curved guide of the counter face, is cut away to form an insert identical in profile to the oval tube. The adapter is painited a dull black to minimize reflectance. The completed device is shown in position on the couinter in figure 1. The value of the adapter has been proven through many bacteriological analyses. The main advantages are as follows: (1) Light contrast permits easy counting with glare eliminated. (2) The tube is held in a fixed central position on the counting plate. Thus, in the case of high count tubes, total counts are not necessary since a factor can be employed in estimating total count from small area analyses.