The complex community of microbes residing in our gut, also known as the gut microbiota, is currently seen as an organ of vertebrate animals which has multiple functions such as contributing to food digestion and protecting the host from pathogens. Our lab is dedicated to the study of the commensal and pathogenic bacterial components of the gut microbiota, and their interactions with each other and the host. An important, secondary goal, is to utilize our knowledge to promote the well being of humans and food animals, such as poultry.
Do gut bacteria utilize the chicken egg for vertically transmission from the hen to the chick?
Early vertical transmission to the chick is theoretically beneficial for bacteria as it would allow access to an empty niche. Early vertical transmission is also theoretically beneficial for the host as the microbiota supports a number of functions for the host, such as degradation of plant derived fiber and protection from pathogens, and these functions are dependent on the host being exposed to the right commensal bacteria. A main mechanism contributing to vertical transmission are the interactions between parents and their progeny. However, in the poultry industry fertilized eggs are separated from the hens immediately after being laid. Thus, the egg is the only connection between the chick and the hen in the poultry industry. Interestingly, many reptiles deposit their eggs and have no interactions with their progeny. Thus, we hypothesized that gut bacteria might utilize the egg for vertical transmission. Our published work, based on 16S rDNA sequencing, shows that material from the gut likely travels the full length of the reproductive tract. This shows that all gut bacteria, and not only pathogens as previously thought, can inhabit and ascend the reproduction tract. Thus gut bacteria are found in the right location to be deposited in the forming egg. Furthermore, gut bacteria are found in the site of fertilization. It is interesting to speculate on the possible effects of bacterial signaling on poultry reproduction and egg laying. We are continuing to study the mechanism and impact of vertical transmission.
Developing a probiotic for poultry to reduce morbidity and enhance production
There are a number of probiotics for poultry available on the market. However, such as in the case of probiotics for humans it is not clear if these probiotics do what they advertise. A part of the problem is that some bacteria used as probiotics were not isolated from the target organism and may not be able to colonize the target organism. Another frequent problem is that the positive effects of some probiotics were demonstrated only in-vitro and not in the target organism. In this project we will first characterize the gut microbiota of poultry, determine which bacteria are good candidates to be used as a probiotic, isolate them, and put them back into newly hatched chicks one by one to determine their effect on the developing chick and its gut microbiota. Not only would we possibly develop a new set of probiotics for poultry, we will also learn about the ability of different bacteria to colonize the gut and about the interactions between different bacteria in the gut community.
Characterization of environmental signals monitored by gut bacteria
Bacteria need to sense changes in their environment in order to survive and optimally utilize available resources. While we can easily identify in bacterial sequenced genomes a large number of environmental sensors (because many of them are enzymes such as histidine kinases or cyclic-di-GMP modulating enzymes) we know very little about what is sensed, how, and when during the life cycle of the bacteria. Understanding sensing will allow as to modal bacterial behavior, better understand the environment (such as the gut environment), develop whole cell biosensors, and develop new anti-bacterials that will work by manipulating bacteria, for example by exposing them to the immune system or to co-administrated antibiotics. In this project we will characterize sensing in high throughput by RNAseq to identify both the signals and the responses. We are starting from the pathogen Salmonella but aim to later expend to other bacteria, including gut commensals.
Characterization of the mechanism of Salicylic acid sensing by Salmonella
Cyclic-di-GMP is an important bacterial second messenger which in many bacteria controls a motility versus sessility and biofilm formation switch. Inhibitors of cyclic-di-GMP and biofilm formation are widely sought as a solution to multiple bacterial problems, from catheter associated infections to food safety. We have previously shown that exposure of Salmonella bacteria to Salicylic acid results in a lowering of cyclic-di-GMP, and a concurrent reduction in the export of cellulose, which is a component of the Salmonella biofilm. In this project we aim to characterize the signal transduction pathway connecting Salicylic acid to cyclic-di-GMP levels. Understanding how this natural inhibitor of Salmonella cyclic-di-GMP and biofilm formation functions will be helpful in the development of natural biofilm inhibitors.