THE SURVIVAL OF BACTERIA EXPOSED TO DESICCATION ON SURFACES ASSOCIATED WITH FARM-BUILDINGS

The survival of 11 species of Gram-negative and Gram-positive bacteria was examined on different surfaces exposed to desiccation. There were large variations between species; Pseudomonas spp. and Rhizobium legu minosarum biovars survived for less than 2 d, whilst Enterococcus spp. survived for more than 11 weeks. The type of surface on to which the bacteria were deposited affected survival, but with different effects between species. In addition the survival of spontaneous nalidixic aci d-resistant (Nal-r) mutants of a natural Escherichia coli isolate were compared. Overall the differences were slight, but of seven resistant mutants, five survived better than the parent whilst one survived les s well. Nine transposon insertion derivatives of one of the Nal-r muta nts (EC080) which survived better than the parent were compared; all s urvived similarly to the parent except EC0883 which survived less well . The growth characteristics of EC0883 and EC080 were compared; at hig h osmotic pressures (> 0.4 mol 1(-1) NaCl) EC0883 grew more slowly and showed a longer lag time than the parent. Of the osmoregulatory funct ions studied, EC0883 appeared to be altered with respect to K+ transpo rt or accumulation, although the transposon insertion had occurred in a gene distant from known K+ transport genes.