Submitted to: The Open Microbiology Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/2/2008
Publication Date: 10/1/2008
Citation: Crippen, T.L., Sheffield, C.L., Andrews, K., Bongaerts, R.J. 2008. Bacterial concentration and diversity within repetitive aliquots collected from replicate continuous flow bioreactor cultures. The Open Microbiology Journal. 2:60-65. Interpretive Summary: A bioreactor is used to model and study the microbial communities within the gastrointestinal tract. Microbial communities help protect animals against invading pathogenic bacteria. Samples of pooled, fresh or previously frozen intestinal material from 7 day old chickens were used to establish cultures in replicate bioreactors. The cultures were maintained under constant growth conditions and the resulting aqueous and the sedentary (biofilm) bacterial elements were characterized. We found minor population differences between the aqueous and biofilm elements and between replicate cultures. Prior studies have shown that storage of culture material as a frozen stock diminishes its ability to protect against invasion by harmful bacteria, such as Salmonella. We introduced Salmonella into the established cultures and monitored its clearance. We determined that despite small differences in bacterial populations, cultures started from both fresh and frozen intestinal material, were able to resist invasion by Salmonella with similar effectiveness.
Technical Abstract: Aims: The aims of this study were to determine if: 1) aqueous and biofilm components within replicate, stabilized bioreactor communities initiated with chicken cecal material differed in diversity; 2) changes in bacterial diversity or diminished protective capabilities resulted from frozen glycerol storage of cecal material stocks; 3) changes in bacterial diversity affect the persistence of Salmonella within the culture. Methods and Results: Replicate bioreactors were established from samples of pooled, fresh or frozen cecal material from 7 d old chicks. After three weeks, aqueous and biofilm components of the stabilized communities were characterized and compared. There were no significant differences in bacterial concentrations, but variations in bacterial diversity were identified. Upon challenge with Salmonella, no significant fluctuations in persistence of the Salmonella were found between the stabilized fresh and frozen derived cultures. Conclusions: We determined that neither the observed differences in bacterial diversity nor storage of material as frozen glycerol stocks affected the ability of the subsequent bacterial community to resist invasion by Salmonella. Significance and Impact of Study: Stabilized bioreactor cultures derived from either fresh or frozen cecal material from 7 d old chicks were capable of clearing a 10**6 CFU ml-**1. Salmonella challenge in less than 3 weeks despite differences measured in bacterial diversity.