The assemblage of bacteria and fungi associated with red imported fire ants (RIFA) Solenopsis invicta Buren was obtained from Hinds, Leake, and Madison Counties (location) along Natchez Trace Parkway in Mississippi. The sites were selected due to the limited presence of RIFA within the park and the more natural, undisturbed ecosystem. Active mounds containing soil, plant debris, and RIFA (substrate) were collected in March, July, and November of 2004 (time). Samples were processed according to standard microbiological protocols, and microorganisms identified using morphological, biochemical and molecular methods. A total of 71 bacteria (2324 isolates) and 50 fungi (1445 isolates) were obtained. The most common bacterium and fungus identified were Bacillus sp. B76(B)Ydz-zz, and Trichoderma aureoviride strain IMI 113135. The fungal entomopathogens Paecilomyces lilacinus and Metarhizium anisopliae var. anisopliae were isolated from mound soil, plant debris, and external tissues of the ants. Patterns of species richness, diversity, and evenness values across substrates were 71, 1.58, and 0.37 for bacteria, and 50, 1.11 and 0.28 for fungi, respectively. Total coefficient of community values for bacteria were 0.74 – 0.89 and 0.79 – 0.92 for fungi indicating uniform communities. No consistent trends were observed by comparing substrate, location, and sampling date. However, fungi species richness and diversity for ant external tissues were significantly higher than internal tissues of the ant. Selected bacteria and fungi were evaluated for their biological control and/or antagonistic potential in vitro and in situ. The most promising isolates studied in vitro included Paenibacillus sp. JA-08, Aspergillus terreus, and Aspergillus sp. HZ-35 with death rates on mound soil surface at 4.4, 5.0, and 4.8. The fungus Metarhizium anisopliae var. anisopliae strain LRC 211 had low death rate (1.8) on mound soil during in vitro trial but showed the greatest biocontrol potential during in situ evaluation. After 14 days in situ evaluation, the living RIFA extracted showed sluggish movement and the fungus was recovered from dead (48.3%) and living (33.3%) RIFA. Since the in situ trials were conducted only at one location and season, additional tests, including microscopic documentation of parasitism/pathogenicity, are needed to confirm the results of this study.

Thelohania solenopsae are intracellular pathogens found in the red imported fire ant, Solenopsis invicta. These pathogens cause detrimental effects to their fire ant hosts. The present study revealed that the midgut and the meconium materials from pupating fourth instar larvae were possible vehicles for the horizontal transmission of the disease. The pathogen was further found to cause a reduction of humeral proteins. In SDS-PAGE stained with silver, several proteins were observed only in controls but not in infected fire ant queens. Different queens were found to have variable proteins reduced due to infection of this pathogen. Furthermore, vitellogenin titers were found to be significantly reduced in infected fire ant queens, although the infection rates of the fat body cells was found to be less than 20%. Finally, although the pathogens did not directly induce apoptosis in infected cells, there were more infected cells undergoing apoptosis than uninfected cells. There was no evidence to support the idea that infected fat body cells became more resistant to apoptosis inducers.

Thelohania solenopsae are intracellular pathogens found in the red imported fire ant, Solenopsis invicta. These pathogens cause detrimental effects to their fire ant hosts. The present study revealed that the midgut and the meconium materials from pupating fourth instar larvae were possible vehicles for the horizontal transmission of the disease. The pathogen was further found to cause a reduction of humeral proteins. In SDS-PAGE stained with silver, several proteins were observed only in controls but not in infected fire ant queens. Different queens were found to have variable proteins reduced due to infection of this pathogen. Furthermore, vitellogenin titers were found to be significantly reduced in infected fire ant queens, although the infection rates of the fat body cells was found to be less than 20%. Finally, although the pathogens did not directly induce apoptosis in infected cells, there were more infected cells undergoing apoptosis than uninfected cells. There was no evidence to support the idea that infected fat body cells became more resistant to apoptosis inducers.