INTRODUCTION TO MICROBIOLOGY Dr Nazia Khan Assistant professor College of medicine Majmaah university

LEARNING OBJECTIVES AFTER STUDYING THIS CHAPTER, YOU SHOULD BE ABLE TO: A. Explain fundamentals of microbiology and its medical importance B. Give brief history of evolution of microbiology with special contribution of Robert Koch and Louis Pasteur C. Describe branches of microbiology D. Describe basic characteristics of bacteria, viruses, parasites and fungi with examples of common diseases

INTRODUCTION  The Science of Microbiology: Introduction  Microbiology is the study of microorganisms(microbes), a large and diverse group of microscopic organisms that exist as single cells or cell clusters; it also includes viruses, which are microscopic but not cellular.  They are responsible for cycling the chemical elements essential for life, including carbon, nitrogen, sulfur, hydrogen, and oxygen; more photosynthesis is carried out by microorganisms than by green plants.  It has been estimated that 5 x microbial cells exist on earth.  Humans also have an intimate relationship with microorganisms; more than 90% of the cells in our bodies are microbes

 The various categories of microbes include viruses, bacteria, archaea, protozoa, and certain types of algae and fungi.

TERMINOLOGIES 1. Mutualism, one that benefits all of the contributing parties 2. Symbiosis: a continuing association of different organisms 3. Parasitism: If the exchange operates primarily to the benefit of one party, the association is described as parasitism, a relationship in which a host provides the primary benefit to the parasite 4. Disease-causing microorganisms are technically known as pathogens (also referred to as infectious agents) 5. The vast majority of known microbes are nonpathogens— microbes that do not cause disease. GLOBAL BURDEN OF DISEASES- WHO 2013

WHY STUDY MICROBIOLOGY 1. We have, living on and in our bodies approximately 10 times as many microbes as the total number of cells Collectively, these microbes are known as our indigenous microflora (or indigenous microbiota) and, for the most part, they are of benefit to us 2. Some of the microbes that colonize (inhabit) our bodies are known as opportunistic pathogens (or opportunists). 3. Microbes are essential for life on this planet. For example, some microbes produce oxygen by the process known as photosynthesis

4. Many microbes are involved in the decomposition of dead organisms and the waste products of living organisms. Collectively, they are referred to as decomposers or saprophytes.  By definition, a saprophyte is an organism that lives on dead or decaying organic matter.  Saprophytes aid in fertilization by returning inorganic nutrients to the soil. 5. Algae and bacteria serve as food for tiny animals 6. Some microbes live in the intestinal tracts of animals, where they aid in the digestion of food

7. Some bacteria and fungi produce antibiotics that 8. Microbes are essential in the field of genetic engineering. such as insulin, various types of growth hormones, interferons, and materials for use as vaccine 9. For many years, microbes have been used as “cell models.” 10. They cause diseases Infectious diseases are leading cause of death in the world and the third leading cause of death in the United States (after heart disease and cancer)

PIONEERS IN THE SCIENCEOF MICROBIOLOGY.  Bacteria and protozoa were the first microbes to be observed by humans. It then took about 200 years before a connection was established between microbes and infectious diseases.  Among the most significant events in the early history of microbiology were i. the development of microscopes, ii. bacterial staining procedures, iii. Techniques that enabled microorganisms to be cultured (grown) in the laboratory, and steps that could be taken to prove that specific microbes were responsible for causing specific infectious diseases. During the past 400 years, many individuals contributed to our present understanding of microbes.

Anton van Leeuwenhoek (1632–1723) Anton van Leeuwenhoek was the first person to see live bacteria and protozoa, “Father of Microbiology,” the “Father of Bacteriology,” and the “Father of Protozoology”. Leeuwenhoek was not a trained scientist.he was a fabric merchant, a surveyor, a wine assayer, and a minor city official in Holland. As a hobby, he ground tiny glass lenses, which he mounted in small metal frames, thus creating what today are known as single-lens microscopes or simple microscopes. During his lifetime, he made more than 500 of these microscopes

Louis Pasteur (1822–1895) French chemist, Below are some of his most significant contributions: 1.While attempting to discover why wine becomes contaminated with undesirable substances, Pasteur discovered what occurs during alcoholic fermentation 2.The theory of spontaneous generation. 3.He discovered forms of life that could exist in the absence of oxygen. He introduced the terms “aerobes”(organisms that require oxygen) and “anaerobes” (organisms that do not require oxygen). 4.He developed the process called Pasteurization to kill microbes

Contn…… 5. He discovered the infectious agents that caused the silkworm diseases that were crippling the silk industry in France. He also discovered how to prevent such diseases. 6. Pasteur made significant contributions to the germ theory of disease—the theory that specific microbes cause specific infectious diseases. 7. Pasteur championed changes in hospital practices to minimize the spread of disease by pathogens. 8. Pasteur developed vaccines to prevent chicken cholera, anthrax, and swine erysipelas (a skin disease). 9. Pasteur developed a vaccine to prevent rabies in dogs and successfully used the vaccine to treat human rabies.

ROBERT KOCH(1843–1910)  German physician 1. He made many significant contributions to the germ theory of disease. For example, he proved that the anthrax bacillus (B. anthracis), was truly the cause of anthrax. He developed Koch’s Postulates 2. Koch discovered that B. anthracis produces spores, capable of resisting adverse conditions. 3. Koch developed methods of fixing, staining, and photographing bacteria. 4. Koch developed methods of cultivating bacteria on solid media. He obtained pure cultures of bacteria. He discovered the bacterium (M. tuberculosis) that causes tuberculosis and the bacterium (Vibrio cholerae) that causes cholera. 5. Koch’s work on tuberculin (a protein derived from M. tuberculosis) ultimately led to the development of a skin test valuable in diagnosing tuberculosis

1. The microorganism or other pathogen must be present in all cases of the disease 2. The pathogen can be isolated from the diseased host and grown in pure culture 3. The pathogen from the pure culture must cause the disease when inoculated into a healthy, susceptible laboratory animal 4. The pathogen must be re- isolated from the new host and shown to be the same as the originally inoculated pathogen

Exceptions to Koch’s Postulates Examples of circumstances in which Koch’s Postulates cannot be fulfilled : A. Certain pathogens will not grow on artificial media. Ex: viruses, rickettsias, chlamydias and the bacteria that cause leprosy and syphilis. Microbes having complex and demanding nutritional requirements are said to be fastidious (meaning fussy). Although certain fastidious organisms can be grown in the laboratory others cannot be grown in the laboratory B. It is necessary to infect laboratory animals with the pathogen being studied many pathogens are species-specific, meaning that they infect only one species of animal. For example, some pathogens that infect humans will only infect humans. Thus, it is not always possible to find a laboratory animal that can be infected with a pathogen that causes human disease

C. Some diseases, called synergistic infections, are caused not by one particular microbe, but by the combined effects of two or more different microbes. It is very difficult to reproduce such synergistic infections in the laboratory. D. certain pathogens become altered when grown in vitro. Some become less pathogenic, whereas others become nonpathogenic. Thus, they will no longer infect animals after being cultured on artificial media. E. not all diseases are caused by microbes

Branches of microbiology  Bacteriology: The study of bacteria  Mycology: The study of fungi  Protozoology: The study of protozoa  Parasitology: The study of parasites  Immunology: The study of the immune system  Virology: The study of viruses  Nematology: The study of the nematodes

GEN CHARACTERISTICS-BACTERIA  Small- Need simple microscope  Prokaryotic  No specific nucleus  One chromosome only  DNA and RNA  No membrane bound organelle  70S ribosome  Replicate by binary fission  Cell membrane without sterol (except Mycoplasma)  Cell wall-Peptidoglycans  e.g. E.coli, Staph aureus

GEN CHARACTERISTICS-VIRUSES  Very Minute- Need electron microscope  Acellular  No nucleus  Either DNA or RNA  Replicates in host cells only  No ribosome  No functional cell membrane  No cell wall  e.g. Human immuno-deficiency virus, Varicella zoster virus

GEN CHARACTERISTICS-FUNGI  Small  Eukaryote  Proper nucleus, nuclear memb  More than 1 chromosome  Mitochondria & other cell bound organelle  80S ribosome  Cell membrane Ergosterol  Complex carbohydrate cell wall –Chitin, Mannan, Glucans  e.g. Candida albicans, Aspergillus

PROPERTIES OF MICROORGANISMS FeaturesVirusesBacteriaFungiParasites Size µ0.3-2µ3-10µ15-25µ# Cell TypeAcellularProkaryoteEukaryote DNA/ RNAEitherBoth Nucleic acid replication Host cellContinuousG & S phase ReplicationComplexBinary fissionMitosis/ Meiosis OrganelleUses hostNot membrane bound Membrane bound RibosomesNone70S(30S+50S)80S(40S+60S) Cell membEnv/Non env No sterol #Mycoplasma ErgosterolCholesterol Cell wallNonePeptidoglycanChitin, Glucan None

Self assessment  Which of the following bacteria was not discovered by Robert Koch? a) Bacillus anthracis b) Mycobacterium tuberculosis c) Salmonella typhi d) Vibrio cholera  The primary use of Koch's postulates is to a) Clearly identify and characterize a particular organism b) Isolate organism from diseased individual c) Demonstrate that the disease is caused by a microorganism d) Develop vaccine for specific disease

 Pasteurization is a process of sterilizing milk and it was discovered by a. koch b. Louis c. Anton d. Newton  Write the exceptions of koch’s postulates  Enlist the different branches of microbiology and their definition  Write the general characterstics of viruses  Write two infectious diseases caused by bacteria,fungi, protozoa and viruses