Assessing Survival of Transgenic Bacteria, Serratia AS1 and Enterobacter cloacae, in Sugar Bait, White Saxaul Plant (Haloxylon persicum) and Rodent Barrow's Soil, A Contained-Field Study for Paratransgenesis Approach.

Background: The viability and persistence of engineered bacterium candidates in field conditions is one of the considerable challenges in the paratransgenesis approach to fighting vector-borne diseases. Methods: In this study two engineered bacterium candidates to produce paratransgenic sand flies, Serratia AS1 and Enterobacter cloacae expressing m-Cherry fluorescent were applied on the leaves of the white saxaul plant (Haloxylon persicum), sugar bait, and rodent burrow soil and their persistent time was tested in desert condition, Matin Abad County, Isfahan, August 2022. A PBS suspension of 109 cells/ml was used for sugar bait, spraying on plant leaves (∼10 cm2) and 10 cm2 of rodent burrow soil. Sand fly samples were taken daily and were plated on LB Agar and the fluorescent cells were counted after 24 hours. Results: Time course in general caused a decrease in the number of bacteria for both strains. The two strains were persistent in sugar bait and on plant leaves for four days and on soil for two days. Although there were slight differences between the number of the bacteria in sugar baits, which was not significant (P< 0.05). The number of E. cloacae surviving on plant and in soil were significantly (P< 0.0001 and P= 0.046) higher than Serratia AS1. Conclusion: This study shows that plants or sugar bait are useful routes for delivery of the transformed bacteria for the paratransgenesis approach, although, the bacteria ought to be sprayed on plants or sugar baits should be replaced with new ones in four days intervals.