9 
or lacking (tet - ) tetracycline. This procedure showed that a substantial 
portion of the bacteria had lost their functioning plasmids. However, at 45 
percent humidity, no difference in numbers of colonies on tet + and tet“ media 
was seen. Ms. Hunt hypothesized that the effects of aerosol izat ion at higher 
humidities, may affect either cellular processes that specifically inhibit the 
tetracycline-resistant mechanisms, or damage the plasmid itself either by 
excision of the gene segments or by replication errors. At lew relative 
humidities the decrease in organism survival due to dehydration may be so 
rapid that other effects are masked . 
At 70 percent relative humidity, no difference in survival between Bacillus 
subtilis BR151 or BR151-pHV14 is seen. Both strains rapidly decreased 99 
percent in survival within five minutes of aerosolization. 
In summary, bacterial survival in aerosols under different environmental 
cord it ions may vary depending on specific organism characteristics. These 
characteristics should be considered in developing control measures. 
Ms. Hunt said the unexpectedly high survival of EL_ coli HB 101-pBRBT at 70 
percent relative humidity necessitates evaluation of survival advantages 
conferred upon the host by each specific reccmbinant plasmid. Such evalua- 
tions would not only provide information for designing proper environmental 
control measures, but might be useful to those interested in increasing airbom 
stability, such as producers of bacterial pesticides. 
Following Ms. Hunt's presentation. Dr. McGarrity asked Dr. Math how the treat- 
ment of exhaust gases in conventional fermentations differs from exhaust gas 
treatment in fermentations using reccmbinant organisms. Dr. Mith replied that 
in conventional fermentations there are no filters in the exhaust lines. 
Dr. Tolin asked Dr. Muth if he knew the relative humidity in the exhaust lines. 
Dr. Muth said he suspected the relative humidity is 100%. He said Eli Lilly 
performs the first two exhaust gas treatments at ambient temperature. The 
temperature is then raised above the dew point for passage through the dry- 
filters . 
Drs. Levin, McKinney, and Tblin agreed the word "prevents" in Appendix K-II-D 
is too restrictive for vsork with the organisms listed in Appendix C. 
Dr. McKinney said that the word is inapprepriate in that the efficiency of 
HEPA filters is 99.97 per cent for particles three-tenths of a micron or larger. 
Dr. Miller offered the following proposals: 
1. that the word "minimizes" be substituted for the word "prevents" in Appendix 
K-II-D, and 
2 . that a statement of the following type be addressed to the RAC: 
"The Guidelines should be amended to explicitly permit latitude by the 
IBC in interpreting Appendix K-II, A through F. Such a decision by the 
IBC should be based on data on the given host-vector combination to be 
fermented. This alteration in the Guidelines may be acconplished by 
amending Appendix C-II, III, IV or Appendix K." 
[345] 
