Lactic acid bacteria produce a variety of bacteriocins that have recently come under detailed investigation. The biochemical and genetic characteristics of these antimicrobial proteins are reviewed and common elements are discussed between the different classes of bacteriocins produced by these Gram-positive bacteria.

Genetics of bacteriocins produced by lactic acid bacteria

Biology, immunology, and cariogenicity of Streptococcus mutans

The production of fermented foods is based on the use of starter cultures, for instance lactic acid bacteria that initiate rapid acidification of the raw material. Recently, new starter cultures of lactic acid bacteria with an industrially important functionality are being developed. The latter can contribute to the microbial safety or offer one or more organoleptic, technological, nutritional, or health advantages. Examples are lactic acid bacteria that produce antimicrobial substances, sugar polymers, sweeteners, aromatic compounds, vitamins, or useful enzymes, or that have probiotic properties.

http://mummified.persiangig.com/new_folder/lact1.pdf

Lactic acid bacteria as functional starter cultures for the food fermentation industry

The cell wall envelope of gram-positive bacteria is a macromolecular, exoskeletal organelle that is assembled and turned over at designated sites. The cell wall also functions as a surface organelle that allows gram-positive pathogens to interact with their environment, in particular the tissues of the infected host. All of these functions require that surface proteins and enzymes be properly targeted to the cell wall envelope. Two basic mechanisms, cell wall sorting and targeting, have been identified. Cell well sorting is the covalent attachment of surface proteins to the peptidoglycan via a C-terminal sorting signal that contains a consensus LPXTG sequence. More than 100 proteins that possess cell wall-sorting signals, including the M proteins of Streptococcus pyogenes, protein A of Staphylococcus aureus, and several internalins of Listeria monocytogenes, have been identified. Cell wall targeting involves the noncovalent attachment of proteins to the cell surface via specialized binding domains. Several of these wall-binding domains appear to interact with secondary wall polymers that are associated with the peptidoglycan, for example teichoic acids and polysaccharides. Proteins that are targeted to the cell surface include muralytic enzymes such as autolysins, lysostaphin, and phage lytic enzymes. Other examples for targeted proteins are the surface S-layer proteins of bacilli and clostridia, as well as virulence factors required for the pathogenesis of L. monocytogenes (internalin B) and Streptococcus pneumoniae (PspA) infections. In this review we describe the mechanisms for both sorting and targeting of proteins to the envelope of gram-positive bacteria and review the functions of known surface proteins.

Surface Proteins of Gram-Positive Bacteria and Mechanisms of Their Targeting to the Cell Wall Envelope

A total of 221 strains of Lactobacillus isolated from meat and meat products were screened for antagonistic activities under conditions that eliminated the effects of organic acids and hydrogen peroxide. Nineteen strains of Lactobacillus sake, three strains of Lactobacillus plantarum, and one strain of Lactobacillus curvatus were shown to inhibit the growth of some other lactobacilli in an agar spot test; and cell-free supernatants from 6 of the 19 strains of L. sake exhibited inhibitory activity against indicator organisms. Comparison of the antimicrobial spectra of the supernatants suggested that the inhibitory compounds were not identical. One of the six strains, L. sake Lb 706, was chosen for further study. The compound excreted by L. sake Lb 706 was active against various lactic acid bacteria and Listeria monocytogenes. Its proteinaceous nature, narrow inhibitory spectrum, and bactericidal mode of action indicated that this substance is a bacteriocin, which we designated sakacin A. Curing experiments with two bacteriocin-producing strains of L. sake resulted in mutants that lacked both bacteriocin activity and immunity to the bacteriocin. Plasmid profile analysis of L. sake Lb 706 and two bacteriocin-negative variants of this strain indicated that a plasmid of about 18 megadaltons may be involved in the formation of bacteriocin and immunity to this antibacterial compound. In mixed culture, the bacteriocin-sensitive organisms were killed after the bacteriocin-producing strain reached maximal cell density, whereas there was no decrease in cell number in the presence of the bacteriocin-negative variant. Images

Antibacterial activity of Lactobacillus sake isolated from meat.

Bacteriocins of gram-positive bacteria.

Introduction to Microbes in Foods History and Development of Food Microbiology Introduction Discovery of Microorganisms Where are they Coming From? What are their Functions? Development of Early Food Microbiology (Before A.D. 1900) Food Microbiology: Current Status Food Microbiology and Food Microbiologists Characteristics of Predominant Microorganisms in Food Introduction Classification of Microorganisms Nomenclature Morphology and Structure of Microorganisms in Foods Important Microorganisms in Food Important Viruses Important Bacterial Genera Important Bacterial Groups in Foods Sources of Microorganisms in Foods Introduction Predominant Microorganisms in Different Sources Normal Microbiological Quality of Foods and Its Significance Introduction Raw and Ready-to-eat Meat Products Raw and Pasteurized Milk Shell Egg and Liquid Egg Fish and Shellfish Vegetables, Fruits, and Nuts Cereal, Starches, and Gums Canned Foods Sugars and Confectioneries Soft Drinks, Fruit and Vegetable Drinks, Juices, and Bottled Water Mayonnaise and Salad Dressings Spices and Condiments Microbial Foodborne Diseases Microbial Growth Characteristics Introduction Microbial Reproduction or Growth Nature of Microbial Growth in Food Factors Influencing Microbial Growth in Food Introduction Intrinsic Factors or Food Environment Extrinsic Factors Microbial Metabolism of Food Components Introduction Respiration and Fermentation during Growth Metabolism of Food Carbohydrates Degradation of Polysaccharides Microbial Sporulation and Germination Introduction Mold Spores Yeast Spores Bacterial Spores Importance of Spores in Food Beneficial Uses of Microorganisms in Food Microbial Stress Response in the Food Environment Introduction Stress Adaptation Sublethal Stress and Injury Viable-but-Nonculturable Proponent Views Microorganisms Used in Food Fermentation Introduction Microbiology of Fermented Foods Lactic Starter Cultures Other Starter Cultures Yeasts and Molds Biochemistry of Some Beneficial Traits Introduction Mechanisms of Transport of Nutrients Transport and Metabolism of Carbohydrates Transport and Metabolism of Proteinaceous Compounds and Amino Acids Transport and Metabolism of Lipid Compounds Genetics of Some Beneficial Traits Introduction Plasmids and Plasmid-Linked Traits in Starter-Culture Bacteria Gene Transfer Methods in Starter-Culture Bacteria Gene Cloning Genome Mapping and Sequencing Starter Cultures and Bacteriophages Introduction History Concentrated Cultures Starter-Culture Problems Yeast and Mold Cultures Microbiology of Fermented Food Introduction General Method of Production Fermented Dairy Products Fermented Meat Products Fermented Vegetable Products Intestinal Beneficial Bacteria Introduction Microbiology of the Human GI Tract Important Characteristics of Beneficial Bacteria Beneficial Effects of Probiotics Some Aspects to Consider Current Developments Food Biopreservatives of Microbial Origin Introduction Viable Cells of Lactic Acid Bacteria as Preservatives Organic Acids, Diacetyl, Hydrogen Peroxide, and Reuterine as Food Preservatives Bacteriocins of Lactic Acid Bacteria as Food Preservatives Yeast Metabolites as Preservatives Food Ingredients and Enzymes of Microbial Origin Introduction Microbial Proteins and Food Additives Microbial enzymes in Food processing Microbial Food Spoilage Important Factors in Microbial Food Spoilage Introduction Sequence of Events Significance of Microorganisms Some Important Food Spoilage Bacteria Significance of Foods Spoilage of Specific Food Groups Introduction Fresh and Ready-To-Eat Meat Products Eggs and Egg Products Fish, Crustaceans, and Mollusks Milk and Milk Products Vegetables and Fruits Soft Drinks, Fruit Juices and Preserves, and Vegetable Juices Cereals and their Products Liquid Sweeteners and Confectioneries Mayonnaise, Salad Dressings, and Condiments Fermented Foods Canned Foods New Food Spoilage Bacteria in Refrigerated Foods Microorganisms that Grow in Refrigerated Foods (Psychotrophs) Popularity of Refrigerated Foods Microbiological Problems Incidence of Spoilage of Vacuum-Packaged Refrigerated Food Food Spoilage by Microbial Enzymes Introduction Characteristics of Heat-Stable Enzymes of Psychotrophic Bacteria Spoilage of Foods with Heat-Stable Microbial Enzymes Spoilage of Foods by Microbial Enzymes at Low Temperature Indicators of Microbial Food Spoilage Introduction Microbiological Criteria Chemical Criteria Assay of Heat-Stable Enzymes Microbial Foodborne Diseases Important Facts in Foodborne Diseases Introduction Human Gastrointestinal Disorder Epidemiological Aspects Current Trends Foodborne Intoxications Introduction Staphylococcal Intoxication Botulism Mycotoxicosis Foodborne Infections Introduction Salmonellosis by Salmonella enterica Listeriosis by Listeria monocytogenes Pathogenic Escherichia coli Shigellosis (Bacillary Dysentery) by Shigella spp Campylobacteriosis by Campylobacter spp Yersiniosis byYersinia enterocolitica Gastroenteritis by Vibrio spp Enteric Viruses Other Foodborne Infections Foodborne Toxicoinfections Introduction Clostridium perfringens Gastroenteritis Bacillus cereus Gastroenteritis Cholera Escherichia coli Gastroenteritis Opportunistic Pathogens, Parasites, and Algal Toxins Introduction Opportunistic Pathogens Biogenic Amines Algal Toxins Parasites New and Emerging Foodborne Pathogens Introduction Associated Factors Miscellaneous Factors Other Emerging Foodborne Pathogens of Concern Indicators of Bacterial Pathogens Introduction Criteria for Ideal Indicators Coliform Group Enterobacteriaceae Group Enterococcus Group Control of Microorganisms in Foods Control of Access (Cleaning and Sanitation) Introduction Objectives of Sanitation Factors to Consider Control by Physical Removal Control by Heat Introduction Objectives Mechanism of Thermal Inactivation Influencing Factors Nature of Food Mathematical Expressions Methods Control by Low Temperature Introduction Objectives Mechanisms of Cold Induced Inactivation Influencing Factors Methods Control by Reduced Water Activity Introduction Objectives Mechanism of Action Influencing Factors Nature of Microorganisms Methods Control by Low pH and Organic Acids Introduction Objectives Mechanisms of Antimicrobial Action Influencing Factors Acids Used Control by Modified Atmosphere (or Reducing O-R Potential) Introduction Objectives Mechanism of Action Influencing Factors Methods Control by Antimicrobial Preservatives Introduction Objectives Influencing Factors Examples of Antimicrobial Preservatives H2O2 Control by Irradiation Introduction Objectives Mechanisms of Antimicrobial Action Influencing Factors Methods Control by Novel Processing Technologies Introduction Summary of Processing Methods Pulsed Electric Field Hydrostatic Pressure Processing Control by a Combination of Methods (Hurdle Concept) Introduction Mechanisms of Antimicrobial Action Current Status Microbial Detection and Food Safety Conventional and Biosensor Based Detection Methods for Microorganisms in Food and Food Environment Introduction Methods Used Standard and Recommended Methods Sampling for Microbial Analysis Quantitative Methods for Microbial Enumeration in Foods Qualitative Methods to Isolate Microorganisms in Foods Test for Bacterial Toxins in Foods Rapid Methods and Automation Biosensors for Pathogen Detection Appendix A: Microbial Attachment to Food and Equipment Surfaces Importance Mechanisms of Attachment Influencing Factors Control Measures Appendix B: Predictive Modeling of Microbial Growth in Food Importance Traditional Methods Predictive Microbiology Appendix C: Regulatory Agencies Monitoring Microbiological Safety of Foods in the United States Food Safety Regulations The Agencies Appendix D: Hazard Analysis Critical Control Points Introduction HACCP Principle of the NACMCF Index

Fundamental food microbiology

Food Biopreservatives of Microbial Origin provides basic and applied information regarding how antimicrobial metabolites of safe, food-grade bacteria (used in food fermentation) can be utilized as food preservatives. The authors discuss why biopreservation of food is important, identify the foods and microoganisms for which biopreservation is suitable, and explore the potential of bacteriocins of food-grade starter culture bacteria and the antimicrobial proteins of yeasts as possible food biopreservatives. The book is a valuable reference resource that will benefit students of food science and researchers in food industries, regulatory agencies, and advisory groups.

Food Biopreservatives of Microbial Origin

"Preface to the Fifth Edition The golden era of food microbiology has begun. All three areas of food microbiology, beneficial, spoilage, and pathogenic microbiology, are expanding and progressing at an incredible pace; thus, it is difficult for one to stay abreast of new developments. A genuine attempt has been made to capture those developments in this new edition. Spoilage-causing microorganisms are a major concern. To feed the growing population in the world, microbial food spoilage must be reduced, and improved intervention technologies must be developed. To achieve that goal, it is necessary to understand the problems; that would help to develop effective control methods for different types of foods, especially using the hurdle concept. In the past decade, foodborne pathogens have broadened their association with varieties of foods that were unexpected, such as Salmonella in peanut butter, fish, and spices; Listeria monocytogenes in cantaloupe and celery; and a new strain of Shiga-toxin producing Escherichia coli (O104:H4) with sprouts. To have a greater understanding of pathogen association in preharvest plants and meat animals, the concerted efforts of plant biologists, animal scientists, soil chemists, environmental scientists, agriculture and biological engineers, social scientists, and microbiologists are needed to address food safety and quality issues"--Provided by publisher.

Genetic Engineering Strategies.- Progress in Genetic Research of Lactic Acid Bacteria.- Cloning and Expression Vectors for Lactococci.- Expression of Human and Murine Interleukins in Lactococcus lactis.- Lactic Acid Bacteria Involved in Food Fermentations and Their Present and Future Uses in Food Industry.- Probiotics of Lactic Acid Bacteria: Science or Myth?.- Use of Bacteriocin Producing Starters Advantageously in Dairy Industry.- Characteristics and Applications of Pediocin(s) of Pediococcus Acidilactici: Pediocin PA-l/AcH.- Polysaccharides, Oligosaccharides, Special Sugars and Enzymes via Leuconostoc Mesenteroides sp. Fermentations.- Role of Lactic Acid Fermentation in Bioconversion of Wastes.- Indigenous Lactic Acid Bacteria of Various Food Commodities and Factors Affecting Their Growth and Survival.- Fermentation Process for the Production of Lactic Acid.- Casein-Breakdown by Lactococcus lactis.- Mechanism of Nisin-induced Pore-formation.- Induction of Penicillin Resistance in S. thermophilus.- Kinetics of Food Processes Involving Pure or Mixed Cultures of Lactic Acid Bacteria.- The Stabilization of Biocatalytic Proteins Against Inactivation.

Bibek Ray

Papers

Bacteriocins of gram-positive bacteria.

Fundamental food microbiology

Food Biopreservatives of Microbial Origin

Fundamental food microbiology

Lactic acid bacteria: current advances in metabolism, genetics and applications