Unit 1 Taxonomy-2-2

Food Microbiology iClass : 

Food Microbiology iClass An Introduction 1

Course Overview: 

Course Overview Unit 1Classification of Microorganisms Unit 2 Indicators in Food Microbiology Unit 3 Foodborne Pathogens Unit 5 Pathogen Evolution 2

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Unit 5 Microbial Growth Unit 6 Microbial Growth in Foods (Hurdle Concept) Unit 7 Thermal and Non-Thermal Processing Unit 8 Sanitation Unit 9 Sampling Plans 3

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Unit 10 Isolation and Enumeration Unit 11 HACCP Unit 12 Microbiology of Food Groups Unit 13 Enteric Viruses 4

Unit 1 Classification of Microorganisms: 

Unit 1 Classification of Microorganisms History of Food Safety Taxonomy of Microorganisms Nomenclature of Bacteria Taxonomy of Bacteria Sources of Microorganisms 5

History of Food Safety: 

History of Food Safety Animals and humans are instinctive in assessing whether a food is safe. Key to the success of human evolution was the ability to produce and store foods to sustain civilized populations. 6

Food Preservation: 

Food Preservation Fundamental techniques in food preservation where known over 10, 000 years ago. Drying Heating Freezing Fermentation Chemical Preservatives 7

Religion and Food Safety: 

Religion and Food Safety In the absence of science religion was the main contact route for populations. Most early religions banned pork (key source of trichinosis parasite). Separation of milk and meat, in additional, to slaughter techniques where advanced food safety initiatives. 8

Microbiology as a Science: 

Microbiology as a Science 1680: Bacteria first observed by Leeuwenhoek using a compound microscope (300 x magnification). Further 200 years before same observations were repeated. Indirect evidence provided the existence of microbes. 9

Antoni van Leeuwenhoek: 

Antoni van Leeuwenhoek Figure 1.2 10

Theory of Life: 

Theory of Life Two Theories Spontaneous generation of life. Microbes are carried or transferred and grow on foods. 11

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Spontaneous life theory survived until early 1800 ’ s. Pasteur using swan necked flasks proved that bacteria where carried in air. 12

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Louis Pasteur: 

Louis Pasteur Figure 1.3 14

Advances in Microbiology: 

Advances in Microbiology Pasteur went onto develop milk pasteurization. Lister 1873 developed first antiseptic Robert Koch: Selective agar and isolation Koch Postulates 15

20th Century: 

20 th Century Antibiotics Freezing Refrigeration Aseptic technologies Irradiation Epidemiology Food Safety Regulation 16

21st Century: 

21 st Century 1970 ’ s Food Microbiology considered an applied science focusing on food spoilage and preservation. Modern times Food Microbiology has split into specialized fields especially in preventing and tracing foodborne illness. 17

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What is Food Microbiology? 18

Taxonomy of Microorganisms: 

Taxonomy of Microorganisms Microorganisms Prokaryotic Eukaryotic Viruses Bacteria Gram Positive Gram Negative Yeast Unicellular Molds Multi-cellular 19

Relative Size of Microorganisms: 

Relative Size of Microorganisms 20

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Broad Classification: 

Broad Classification The Good (Fermentations) The bad (Spoilage) And the very bad (Foodborne illness) 22

The Good: 

The Good Food Production Lactic Acid Bacteria: Yoghurt, Cheese Yeasts: Bread, Beer Mold: Cheese, Single Cell Protein (SCP) Antibiotics Bioremediation 23

The Bad: 

The Bad Food Spoilage Blowing of cans and packaging Off odors and flavors Pigmentation Slime formation 24

The very bad: 

The very bad Disease causing Bacterial mold Protozoa Virus 25

Classification of Microorganisms: 

Classification of Microorganisms Taxonomy - study of the classification, organization, and naming of living things. (similarity) Phylogeny - relationships between organisms. (evolutionary links) Phenotype Genotype 26

Classification based on phenotype: 

Classification based on phenotype 27

Methods of classification: 

Methods of classification Morphology (microscopic analysis) 28

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Differential stain (gram stain, capsule stain, etc.) Purple Red/Pink 29

Biochemistry (catabolic and anabolic pathways) : 

Biochemistry (catabolic and anabolic pathways) Specific enzymes: Catalase, Oxidase Metabolic Products: e.g. fermentation Sugar Utilization (API identification kits) Growth characteristics (temperature, anaerobe) 30

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Serology (specific antibodies) Flagella Receptors Toxins Phage typing (specific binding and lysis of bacteria) 31

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Amino acid sequencing (SDS PAGE) Fatty acids Flow cytometry (differences in electrical conductivity) 32

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Development of more sophisticated techniques has led to re-evaluation of bacterial taxonomy Bergey's Manual of Systematic Bacteriology still regarded as the foundation for classifying bacteria 33

DNA: 

DNA 34

Genotyping: 

Genotyping How similar are microorganisms at the DNA level. Evolutionary links Mutations in DNA increase evolutionary distance 35

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DNA hybridization Complementation of DNA strands DNA sequencing e.g. 16S rRNA 36

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The 16S rRNA gene : The most useful molecule for determining evolutionary relationships. General sequence highly conserved but point mutations slowly occur over time. Sequence provides a measure of evolutionary distances 37

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16S rRNA Domain I Domain II Domain III Domain IV 38

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Secondary Structure the Same but Sequence Differs 39

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A AC G T C GAAA (Organism A) A AC CT C GAAA (Organism B) A GG CT A GAAA (Organism C) A GG CT A G T AA (Organism D) AB: 1 different AC: 3 different CD: 1 different AD: 4 different BD: 4 different 40

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Evolutionary relationships of representative bacteria based on the sequences of their 16S rRNA genes 42

Major Groups of Bacteria: 

Major Groups of Bacteria 43

Naming of Bacteria: 

Naming of Bacteria Phenotypic characteristic Place name Source of original isolation Person who discovered 44

Classification: 

Classification Kingdom: Procaryote Phylum: Gracilicutes Class: Scotobacteria Family: Enterobacteriaceae Genus: Escherichia Species: coli 45

Nomenclature of Bacteria: 

Nomenclature of Bacteria Escherichia coli ATCC 13704 GENUS SPECIES ID number Names usually derived from latin or Greek coli- belonging to colon Escherichia : named after Escherich who discovered the bacterium in 1895 Abbreviated to E. coli Underline or italic species name not capatilized 46

Salmonella is an exception : 

Salmonella is an exception Salmonella composed of closely related serovars Genus Salmonella has only one species Salmonella enterica Therefore, serotypic names are used E.g. Salmonella Tyhimurium 47

Sources of Microorganisms: 

Sources of Microorganisms Primary Sources are any environment that permits growth and survival Environment Soil Plants Water 48

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Animals Hide/skin Intestinal tract The ability of microorganisms to utilize nutrient sources, compete with other microflora and survive environmental stresses is key. 49

Routes of Transfer: 

Routes of Transfer Air Water Contact 50

What do Food Microbiologists do?: 

What do Food Microbiologists do? Study microbes that inhabit, produce or contaminate foods. Establish criteria to establish if a food or environment is microbiological acceptable. Develop and review policy to ensure the safety of foods. Validate and verify intervention methods to ensure the stability and safety of foods. Provide information to the public on food safety. 51

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Microbiology Economics Risk Analysis Policy and Regulations Process Engineering Molecular Biology Management and Communica-tions Molecular Biology Food Microbiology 52