Jose Bruno-Barcena
Assistant Professor
Biomanufacturing Training & Education Center

Lactic acid bacteria; physiology, genetics and bioprocessing

Research Brief

There is a long history of the healthy beneficial effects associated with live microorganisms present in food.  The association between intestinal colonization and susceptibility to disease as well as the study of processes in which microoganisms have a role, specifically those related with food products, are of special interest in the area of microbiology and for the food industry.  As a result, there is a movement towards the development of new functional food products and their introduction into the market place.  My primary research interest is to investigate and to implement a research program in different, but complementary areas of study with a focus on functional probiosis.  The objective will be to understand the phenomena, but with some emphasis on practical applications (e.g., the generation of safer foods).  We are particularly fascinated in understanding the molecular genetic basis underlying the development of stress tolerance responses among gut microbiota.  The final goal will be to understand the physiological and molecular basis for probiosis / pathogenesis in gut microbiota.

One of our past research projects was the identification and study of loci implicated in the oxidative stress response.  The general oxidative defense mechanisms that are found in the enterobacteria group differ in part from that found in the lactobacilli group.  Analyzing the lactobacilli group, we have identified that the presence of a heterologous superoxide dismutase improves the fitness of the population growing in aerobic conditions.  Such changes in gene content can provide us with valuable insight into the genetic basis of lifestyle differences among probiotic / pathogens and also with the basic knowledge to improve technologically important strains.

Based on these studies, we are dissecting the underling mechanisms of stress response and characterizing regulons and gene regulators in lactic acid bacteria that clearly differ from the traditional enterobacteria models.  Recently, we used the necessary tools that allowed us to genetically manipulate these Gram positive strains.  In this context, here at North Carolina State University we were able to perform insertional mutagenesis in Lactobacillus gasseri that resulted in the validation of the method for functional gene replacement.  A method previously constructed and tested for insertional inactivation by Russell and Klaenhammer (2001) was employed for this project.  This technique, if it can be further refined, has enormous potential for both forward and reverse genetic approaches to studying gene function.  Finally, this will allow for the improvement in either technological characteristic of probiotic organisms or in the discovery of new targets in the war against the pathogenic microbiota.  

In addition to the molecular approach outlined above, I would also like to integrate physiological work into my research in order to better understand the molecular basis of the interaction between microorganisms and explore the practical applications.  It has been proposed that microorganisms in nature exist as biofilms, as they are found in the gut, while free cell culture techniques only represent laboratory artifacts.  One of my past research projects was the setting up and optimization of immobilized operational systems.  In immobilized cell reactors, the biological organism or catalyst is kept fixed in a natural or artificial matrix, while substrates and products are continuously flowing through in the mobile phase.  These enabled us to work with bacteria naturally attached to inert supports.  These biofilm operational systems reproduce more closely the behaviour of the bacterial strains in nature or in our case the gut biofilm formation and maintenance.  Therefore, a more controlled environment could facilitate the study of gene pattern expression implicated in stress responses, or in the conditions closely mimicking what the strains endure in the environment.  Traditionally, such studies have been difficult since gut microflora is highly enriched in different microbiota.  However, modern molecular and culture techniques such as, immobilization will allow us for controlled pure or mixed growing cultures to be studied.

Biographical Sketch

Curriculum Vitae