The Aerosol Survival and Cause of Death of Escherichia coli K12

Abstract

SUMMARYThe survival of Escherichia coli K 1 2 HfrC sprayed from distilled water into a nitrogen atmosphere as a function of aerosol age and of storage relative humidity (RH) is demonstrated. The survival pattern was typically that of E. coli, i.e. marked instability in a region at high RH and better stability at low RH. The results of changing the RH from the storage RH to IOO % or 30 % are described. Comparison of survival in nitrogen with that in air showed air to be slightly toxic, the toxic component being oxygen or a trace of some contaminant in it. Glycerol and rafhose were slightly protective as additives at high RH; at low RH glycerol was toxic, but rafhose was highly protective. It was discovered that E. coli K I~ HfrC carried a temperate phage and that this phage was not activated by the processes involved in aerosol experiments. The synthesis of phages T3 and p2 by E. coli K I~ HfrC, collected from the aerosol, was examined. Phage production and viability were similar, and hence it is concluded that in a nitrogen atmosphere loss of viability was not caused by DNA inactivation, DNA synthesis inhibition or inhibition of cellwall division, but by failure of RNA synthesis, protein synthesis or energy production.

The Effects of Oxygen on the Possible Repair of Dehydration Damage by Escherichia Coli

“…Throughout these investigations differences seemed to exist between the behaviour of the two strains of Escherichia coli used and that of E. coli K 12 as reported by Cox (1968). Both of the strains used here were stable at relative humidities above 80%, which contrasted with the behaviour of the E. coli K I~ strain used by Cox, which apparently is unstable in aerosols at high RH values.…”

“…Most investigators have found organisms held at 25" and at relative humidities above 75% to be stable. In contrast, however, Cox (1967Cox ( ,1968 found that Escherichia coli died rapidly when held in an atmosphere of nitrogen at relative humidities between 85 and 75%.…”

“…The apparent difference between the behaviour at 80% RH of the two strains of Escherichia coli used here and that used by Cox (1968) may be due to the condition of the air existing in respective laboratories or the purity of the nitrogen used. Alternatively, the strain used by Cox may lack a repair system or its prophage may be a defective one.…”

Aerosol survival of Serratia marcescens as a function of oxygen concentration, relative humidity, and time

“…Hence, if species A.izH,O does exist in bacteria, it would exist in an environment which contains much weakly bound water. Such an environment would occur in the interspace between the cytoplasn~ic membrane and the cell wall and this possibility is consistent with data obtained from entirely different experiments, which suggested that cell wall synthesis and (or) cell division are probably inhibited through the toxic action of oxygen (6,9,11). Furthermore, the relationship between 1 and a, explains the apparent lack of a toxic action of oxygen at high RH, because reaction rate depends upon concentration, and provided that the concentration (moles per liter) is very small, then the rate of reaction will also be very small.…”

Bioaerosol generation by raindrops on soil

“…While it has been generally accepted that soil can serve as an intermediate home for pathogens before they transfer to their hosts, it is not clear where and how the microbes in the soil transfer from their original habitats to the atmosphere2122232425. Considering that most microbes prefer aqueous environments to survive, it is still a mystery to explain how viable soil-based microbes spread much further and faster than would be expected through the air12627. Futhermore, even though we know that after a rainfall there is a rapid increase of bioaerosol concentration in the air, we have not explained the wide spread of microbes with the transfer modes discovered to date92829.…”