Studies to determine the effect of various concentrations of sodium nitrate and ammonium chloride on the ability of Rhizobium meliloti to infect and fix nitrogen in three varieties of alfalfa indicated that nodulation was inhibited at high levels of combined nitrogen. High nitrate concentrations inhibited nodulation to a greater extent than high ammonium concentrations. A small amount of combined nitrogen, however, appeared to promote nodulation. Inoculated plants grown in nitrogen levels which might be encountered in the field consistently contained more nitrogen than uninoculated plants under the same treatment. There was comparatively little difference in the nitrogen content or behaviour of the varieties of alfalfa tested.

The Virtanen technique was used to detect effective and ineffective rhizobia. The rhizobia studied varied widely in their action towards different varieties of the same host species. Maximum leghemoglobin concentrations occurred just prior to blossoming in field legumes, but much earlier in greenhouse legumes cultivated under conditions of this experiment. The nodules of the ineffective strains of legume bacteria differed from those produced by effective strains in color, size, distribution, rate of destruction of the bacteroid area, and presence or absence of rodlike bacterial forms. Experimental evidence is presented to show that a supposedly parasitic strain of alfalfa organism can exist.

Six hundred and sixteen Gram-negative bacterial isolates were obtained from trees and orchards diseased with fire blight. By serological means, 194 Erwinia amylovora isolates were distinguished from 57 nonpigmented isolates of miscellaneous colonial types. One hundred and eighty-nine isolates were distinguished by yellow colony color. In addition, 176 isolates produced a fluorescent pigment. Four other biochemical tests were applied to the isolates.All of the E. amylovora isolates, 26 'miscellaneous white' isolates, and 94 'yellow' isolates were lysed by one or more of seven phages. Two phages, 1507 and 1508, lysed many isolates from all three groups, and in this way relationships were indicated. Phage sensitivity was not correlated with other characteristics, although phage P19 lysed most of the E. amylovora isolates and none of the yellow. Phage P17 lysed a majority of the 'yellow' isolates and none of the E. amylovora. Both phages lysed some 'miscellaneous white' isolates.

Forty microbial types, in which micrococci predominated, were found as representative of pre-curing contamination, including strains resembling organisms found in bacon slime.Varying degrees of salt tolerance were noted, micrococci showing the greatest ability to grow at higher concentrations. With 25% sodium chloride only two species showed growth. Tests with species reducing nitrate to nitrite at 5% salt concentration showed that as the salt concentration increases, nitrate reduction occurs with a progressively smaller proportion of those showing growth. This suggests that nitrate reduction in curing pickle is a function of the true halophiles rather than of the pre-curing contaminants.The organisms could be placed in five groups depending upon their salt resistance (ability to survive) in salt solutions and in curing pickle. Much greater resistance to salt was displayed in curing pickle than in salt broths of similar sodium chloride content. Pickle appeared to possess substances tending to neutralize the toxic effect of salt, the action being "protective" rather than "stimulative".Many types of bacteria constituting original contamination are considered able to survive the pickling process. Although the findings do not point to any pronounced activity of these in pickle, their ability to survive opens the possibility of their becoming active after pickling and contributing to storage defects. The results justify the adoption of measures for the utmost plant sanitation in Wiltshire processing.

A deli-lite variation in sensitivity to gamma racliation was found anlong 18 Snlmonella species co~nmonly occurring in frozen whole egg. The dose levels required for a 10'-fold reduction of these species ranged from 0.36 Mrad t o 0.51 Mrad. Variation in sensitivity to radiation was also detected with three cultures of S . pzillorl~v~ which appeared similar except in origin. Variation in sensitivity within all species of Salnzon~lla studied apparently inclicates that 110 one species can be considered most resistant. These studies reveal that a level of 0.54 Mrad of gamma radiation would reduce the salmonellae t o a safe level in frozen egg. As a result, the product treated by the above method could be commercially acceptable and present no public health problem with respect t o salmonellae.