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Better understanding bacteria moderate amounts might make a significant contribution to human health. DR MARIA MARCO Dr Maria Marco discusses her research into the interactions of bacteria with their environments and the potential to exploit this knowledge to improve our health and prevent the spread of foodborne diseases How did these challenges inspire the creation of your study? This investigation is motivated by our current lack of knowledge on how diet and food delivery matrices – capsules, yoghurt, juice and so on – can influence probiotic functionality in the intestine. Because probiotics should be alive at the time of administration, and bacteria adapt rapidly to changes in their environment, it is likely that these factors are important for predicting and controlling how well the probiotics survive and express the relevant cell compounds necessary for health outcomes. Can you outline the current state of research into the mechanisms of probiotic bacteria? What specific knowledge gaps or questions remain? Strains of Lactobacillus and Bifidobacterium have long been studied for beneficial contributions to health when consumed in food and beverage products. However, many questions remain concerning strain-specificity, and the dosage, frequency and duration needed for the intended effects. A critical step towards answering these questions and evaluating the overall efficacy of the probiotic approach is to elucidate the specific molecular mechanisms by which these bacteria can alter epithelial and immune cell responses in the intestine to generate systemic physiological effects. This research is demonstrating that – much like human pathogens – beneficial or probiotic bacteria synthesise specific products that are able to interact with intestinal cell surface receptors and alter signalling pathways in the host. The number of investigations into probiotics is now increasing rapidly. This growing interest is at least partly the result of renewed understanding about the significant impact of indigenous intestinal microbiota on human health and wellbeing. Because Lactobacillus and Bifidobacterium are common inhabitants of the human digestive tract, it is increasingly conceivable that even dietary bacteria consumed in only Our specific objectives are to compare the effects of different probiotic delivery formats and host diets on Lactobacillus persistence and gene expression in the digestive tract and ability to protect against intestinal inflammation. To start to elucidate differences in Lactobacillus performance we are also identifying changes to the composition of the indigenous intestinal microbiota that might occur in response to Lactobacillus, diet and inflammation. There has been a rise in consumer interest in probiotic bacteria in recent years. What role do they play in improving human health? Numerous studies have shown that the intestinal microbiome is very important for multiple facets of human health. The roles of the indigenous intestinal microbiota include food digestion; energy harvest and detoxification; vitamin production; prevention of infectious disease; and the development and maintenance of the intestinal epithelium and the immune system. The proposed general mechanisms of probiotics are similar to those known for the indigenous microbiota in the human gut. The health benefits found for certain strains encompass both gut-specific and systemic effects. Clinical studies and meta-analyses have concluded that probiotics may be helpful in the prevention and treatment of infectious or antibiotic-associated diarrhoea and in the prevention of excessive inflammatory responses in the intestine. Postdoc Sybille Tachon worked on the probiotics project, and PhD student Tom Williams worked on the food safety project. How does your food safety research – and particularly your work on pathogenic Escherichia coli O157:H7 – connect to the study of probiotic bacteria? All plant surfaces are colonised by commensal (non-pathogenic) bacteria, and this plant microbiome is analogous to the intestinal microbiome. While we are not yet certain of the ways they affect the plant host, the potential exists for the indigenous plant microbiota to alter the survival of pathogenic E. coli O157:H7. Analogous to our findings on the intestinal microbiota, the work is revealing that plants are colonised by diverse bacteria. Bacterial diversity changes with the age of the plant and season of planting. Specific strains isolated from plant surfaces might be particularly useful to prevent E. coli outbreaks associated with fresh produce. What impact do you expect the outcomes of your project to have on policy makers and the food industry? Currently, the term ‘probiotic’ is often misused in labelling and advertising to include regular (fermented) food products and other applications such as soil amendments and household cleaners. This diminishes the potential to advance the concept of probiotics for both healthy and ill individuals. The investigation and its outcomes can influence policy and regulators to restrict product labelling requirements and necessitate experimental substantiation of the strains added to those products. Moreover, the work impacts the food industry by providing essential knowledge on probiotic performance in different delivery matrices that will be useful in the design of food and beverage products containing probiotic bacteria. WWW.RESEARCHMEDIA.EU 109 DR MARIA MARCO Bacteria, food safety and health to utilise the nutrients available in the intestine. However it is uncertain how this will change depending on the other microbes present and the food delivery format of the probiotic. Therefore, the researchers are focusing on how diet and the delivery format of one type of LAB, Lactobacillus, affects its performance in the digestive tract. The investigations are targeting the anti-inflammatory effects of Lactobacillus, as well as how and to what extent they are shaped by host diet and food delivery matrix. Dr Maria Marco and her colleagues from the Department of Food Science and Technology at the University of California, Davis are transforming the way we think about bacteria with in-depth research into the varied roles they can play in food safety and health Innovative gene-targeted approaches are being used to examine these interactions and identify the specific mechanisms that generate probiotic effects. One such approach is the use of high-throughput DNA sequencing to study the intestinal microbiota before and after probiotic consumption. Marco explains why the technique of high-throughput DNA sequencing was chosen for this work: “We rely on this method because standard culturing methods are not able to accurately detect the majority of microorganisms in the intestine and DNA sequencing is a relatively rapid technique to assess the diversity of bacteria inhabiting the gut”. The efficiency of this method is particularly useful because the microbes colonising the digestive tract are distinct for every individual and therefore no two digestive systems will contain the same types and/or quantities of bacteria. IT IS HARD to understate the importance of microoganisms to food supply chains and human health. While outbreaks of pathogens can cause illness, small doses of some bacterial strains can aid digestive health: bacteria such as Lactobacillus and Bifidobacterium, for example, play a beneficial role in human digestive systems. They help to keep the immune systems healthy and facilitate the breakdown of food into useful energy and nutrients. Awareness of the health benefits of these probiotic bacteria has grown in recent years leading to their addition to food and drink products, of which the best known is perhaps probiotic yoghurt. The demand for such products is rising but our understanding of the full potential of bacteria in improving food safety and health remains limited. Dr Maria Marco and her laboratory in the Department of Food Science and Technology at the University of California (UC), Davis are exploring the interplay between diet and food formats on the effectiveness of probiotic food products as well as investigating the roles of commensal bacteria on the safety aspects of fresh produce. The unifying theme behind the work at the laboratory is the role played by lactic acid bacteria (LAB) in food production and digestion. LAB are found on plant surfaces and in human and animal intestines. LAB are used widely throughout the food production system, particularly in the fermentation SCANNING ELECTRON MICROGRAPH OF LACTOBACILLUS CASEI 110INTERNATIONAL INNOVATION of yoghurt, cheese, olives and sourdough bread, and have an important role in shaping fermented food taste and texture. The team is exploring the beneficial effects of LAB and other commensal microorganisms in our foods to improve microbial food safety and human health. BOOSTING BENEFICIAL BACTERIA The general consensus among experts is that probiotic bacteria must be alive when they reach the human gut if they are to have optimal effects on our health. However, these microbes respond quickly to changes in their environment, which has important consequences for the effectiveness of probiotics both before and after consumption. For example, Lactobacillus is currently added to a number of different foods, from yoghurts and cheeses to chocolate and cereal bars; to date, little is known about how these formats affect the molecular interactions between the bacteria, food and host. As such, it is not possible to ensure the consistency of their effects on health. Moreover, LAB must be packaged, transported and stored before they even begin to negotiate the individual conditions of each human digestive system. The group has conducted an extensive review of studies in this area and found that relatively little research has been conducted into how these pre-consumption factors affect the efficacy of dietary probiotic bacteria. Another important facet to probiotic foods is the role that differences in diet have in shaping their impact on human health. Diet has major consequences on health including the development of chronic diseases (eg. Type 2 diabetes mellitus and heart disease). Recent studies have shown how diet also shapes the composition of the indigenous microbiota residing in the intestine. These bacteria outnumber somatic cells in the human body by 10 to one. What is not known is how diet also affects the efficacy of probiotic bacteria that enter the gut through foods and beverages. Prior research has shown that probiotics adapt Using the groundbreaking DNA sequencing technology, it has been possible to identify which microorganisms in the intestines were most changed by diet, the delivery matrix and ingestion of Lactobacillus. This breakthrough will enable the design and production of probiotic food products which better accommodate these complex interactions. It will also improve standards of future investigations: “The findings of the research thus far show that diet should be recorded and possibly standardised in clinical studies intending to assess probiotic effects,” clarifies Marco. These results are being disseminated to the public and food science, nutrition and health industries through conferences, peerreviewed publications and the media. PREVENTING PATHOGENS Much like the intestinal microbiota and probiotics are important to human health, the indigenous bacteria on plants might be doing a similar function. The DNA sequencing technique is being used to establish how the biotic conditions of Romaine lettuce leaves change according to different temperatures and moisture levels both in the field and in controlled growth-chamber studies. These DNA analyses have revealed information about cell activity as well as the diversity and abundance of different microorganisms on lettuce. This successful approach of analysing how environment affects the bacterial diversity INTELLIGENCE MICROBIOTA INFLUENCE ON FOOD SAFETY AND HEALTH Innovative gene-targeted approaches are being used to identify the specific mechanisms that generate probiotic effects OBJECTIVES • To study the effects of native microbiota inhabiting fresh produce on human pathogens which might come into contact with those plants in the field • To study molecular mechanisms of probiotic bacteria beneficial effects on health and the influence of diet on the bacterial residents of the mammalian gut KEY COLLABORATOR Linda J Harris, Department Food Science & Technology, UC Davis, USA FUNDING US Department of Agriculture, National Institute of Food and Agriculture, Agriculture and Food Research Initiative Competitive Grants Program - grant nos 2012-67017-30219 (nutrition and health) and 2010-6520120572 (food safety) CONTACT Dr Maria Marco Principal Investigator Food Science & Technology Department University of California, Davis Office location: 1136 RMI North One Shields Avenue 392 Old Davis Road, Davis California 95616 USA ROMAINE LETTUCE GROWING IN THE SALINAS VALLEY, CALIFORNIA T +1 530 752 1516 E [email protected] www.marcolab.net and activity on a molecular level is also being applied to improve food safety, for example regarding Escherichia coli O157:H7, the wellknown pathogen which can be transmitted through food, and can cause severe illness even in very small doses. Numerous outbreaks of E. coli O157:H7 have been linked to the contamination of leafy green vegetables before they are harvested. Work is underway at the Marco Lab to explore the influence of the indigenous plant microbiota and abiotic environmental variables – in particular extremes and fluctuations in moisture and temperature – on E. coli endurance. The upshot of this project is that farmers will be able to tailor their methods to reduce the likelihood of outbreaks of this pathogen. THE FUTURE OF FOOD The studies carried out so far have revealed a wealth of potential for further investigations into other microbiota and their influence on our health and food safety. Marco points out that the laboratory is also keen to continue expanding knowledge on probiotic bacteria: “The next steps will be to investigate whether the results of this project are transferrable to other strains and foods. Other health benefits should be investigated in light of our comparative analysis on the effects of diet on probiotic performance in the digestive tract”. There are many other strains of bacteria to investigate; studies conducted so far have only begun to scratch the surface. This also applies to using members of the indigenous plant microbiota as sentinels for human pathogens on agricultural crops. From the farm to the human body, understanding how different bacteria respond to a variety of environments at a molecular level is vital to creating healthier and safer food products, and the studies are set to contribute significant knowledge to this field. DR MARIA MARCO is Assistant Professor in the Department of Food Science & Technology, University of California (UC), Davis. She received her BSc in microbiology from Pennsylvania State University (1995) and PhD on plantmicrobe interactions at the University of California, Berkeley (2002). In 2008, she initiated her laboratory at UC Davis to study the molecular genetics, ecology and host-microbe interactions of lactic acid bacteria in food systems and the mammalian digestive tract. WWW.RESEARCHMEDIA.EU 111