INTRODUCTION TO MICROBIOLOGY

Dr Nazia KhanAssistant professorCollege of medicineMajmaah university

LEARNING OBJECTIVES

AFTER STUDYING THIS CHAPTER, YOU SHOULD BE ABLE TO:A. Explain fundamentals of microbiology and its medical

importanceB. Give brief history of evolution of microbiology with special

contribution of Robert Koch and Louis Pasteur C. Describe branches of microbiologyD. 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 1030 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.

TERMINOLOGIES1. Mutualism, one that benefits all of

the contributing parties 2. Symbiosis: a continuing

association of different organisms3. 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

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 us2. 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 animals6. Some microbes live in the intestinal tracts of

animals, where they aid in the digestion of food

7. Some bacteria and fungi produce antibiotics that8. 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 physician1. 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 laboratoryB. It is necessary to infect laboratory animals with the

pathogen being studiedmany 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

Features Viruses Bacteria Fungi ParasitesSize 0.02-0.3 µ 0.3-2µ 3-10µ 15-25µ#Cell Type Acellular Prokaryote Eukaryote EukaryoteDNA/ RNA Either Both Both BothNucleic acid replication

Host cell Continuous G & S phase G & S phase

Replication Complex Binary fission Mitosis/ Meiosis

Mitosis/ Meiosis

Organelle Uses host Not membrane bound

Membrane bound

Membrane bound

Ribosomes None 70S(30S+50S)

80S(40S+60S)

80S(40S+60S)

Cell memb Env/Non env

No sterol #Mycoplasma

Ergosterol Cholesterol

Cell wall None Peptidoglycan Chitin, Glucan

None

Self assessment Which of the following bacteria was not discovered by Robert

Koch?a)      Bacillus anthracisb)      Mycobacterium tuberculosisc)       Salmonella typhid)      Vibrio cholera The primary use of Koch's postulates is toa) Clearly identify and characterize a particular organismb) Isolate organism from diseased individualc) Demonstrate that the disease is caused by a microorganismd) Develop vaccine for specific disease

Pasteurization is a process of sterilizing milk and it was discovered by

a. kochb. 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