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Introduction to Microbiology CLS 245. What is Microorganism? Microorganisms ( or Microbes) are vey small organism that can’t be seen by naked eyes. However,

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Presentation on theme: "Introduction to Microbiology CLS 245. What is Microorganism? Microorganisms ( or Microbes) are vey small organism that can’t be seen by naked eyes. However,"— Presentation transcript:

1 Introduction to Microbiology CLS 245

2 What is Microorganism? Microorganisms ( or Microbes) are vey small organism that can’t be seen by naked eyes. However, these Microbes can be seen with the aid of microscope. These microorganisms can be divided into 4 subgroups: Bacteria,, Fungi, Viruses and Parasites. Microbiology is a broad field that include the study of all types of microorganisms.


4 Cont.. Medical Microbiology is the study of microorganisms: – Bacteria – Fungus – Parasites – Viruses – Most can only be seen with the microscope!

5 Cont.. Medical Microbiology studies are usually performed on human blood and body fluids. Microorganisms can cause disease in humans. Microbiologists determine the type of microorganism causing the disease and find a drug, usually an antibiotic, to inhibit the microorganism. Microbiologists continue to study the microorganisms through research to determine new antibiotics

6 Cont.. Microorganisms are studied in clinical hospital laboratories, reference laboratories, and research facilities.

7 Prokaryotes vs Eukaryotes Before getting into Microbiology, it is important to understand the differences between Prokaryotes and Eukaryotes.

8 Prokaryotes vs Eukaryotes

9 Viruses -Virology is study of viruses. -Viruses are very small microorganisms (smaller than bacteria) and they can’t grow or reproduce apart from living cells. -They are too small to be seen by microscope. -Viruses are not alive, why?

10 Viruses Viruses have wide variety of structure but they all share 2 important element: Genetic material (DNA or RNA) Protein coat or capsid

11 Fungi  The study of fungi is called Mycology.  The fungi are a group of eukaryotic microorganisms, some of which are capable of causing superficial, cutaneous, subcutaneous, or systemic disease.  However, some fungi are also directly important as a food for human (making a bread) or as a treatment ( producing penicillin).

12 Fungi cont Mykes (Greek word) means Mushroom. Fungi are eukaryotes, differ from bacteria and other prokaryotes. Fungi digest dead organic matter. Molds and mushroom are multicellular while Yeast are unicellular Yeast: unicellular fungi Molds: Multicellular fungi


14 Parasites Medical parasitology: “the study and medical implications of parasites that infect humans” A parasite: “a living organism that acquires some of its basic nutritional requirements through its intimate contact with another living organism”. Parasites may be simple unicellular protozoa or complex multicellular metazoa Eukaryote: a cell with a well-defined chromosome in a membrane-bound nucleus. All parasitic organisms are eukaryotes Protozoa: unicellular organisms, e.g. Plasmodium (malaria) Metazoa: multicellular organisms, e.g. helminths (worms) and arthropods (ticks, lice)

15 Cont. Parasite Host: “the organism in, or on, which the parasite lives and causes harm” Intermediate host: “the organism in which the parasite lives during a period of its development only” Vector: “a living carrier ( arthropod) that transports a pathogenic organism from an infected to a non-infected host”. A typical example is the female Anopheles mosquito that transmits malaria

16 What are bacteria? Single celled organisms Very small Need a microscope to see Can be found on most materials and surfaces –Billions on and in your body right now E. Coli O157:H7 can make you very sick. Streptococcus can cause strep throat. This E. coli helps you digest food.

17 What do they look like? Three basic shapes –Rod shaped called bacilli (buh-sill-eye) –Round shaped called cocci (cox-eye) –Spiral shaped Some exist as single cells, others cluster together Bacilli Spiral Cocci Cluster of cocci

18 Bacteria are ALIVE! What does it mean to be alive? –They reproduce (make more of themselves) –They need to eat

19 How do bacteria eat? Some make their own food from sunlight—like plants Some are scavengers –Share the environment around them Example: The bacteria in your stomach are now eating what you ate for breakfast Some are warriors (pathogens) –They attack other living things Example: The bacteria on your face can attack skin causing infection and acne Photosynthetic bacteria Harmless bacteria on the stomach lining E. Coli O157:H7 is a pathogen

20 What is a pathogen? Bacteria that make you sick –Why do they make you sick? To get food they need to survive and reproduce –How do they make you sick? They produce poisons (toxins) that result in fever, headache, vomiting, and diarrhea and destroy body tissue

21 Where do you get a pathogen? Contact with people who are sick –Direct or indirect Food, Water, or other Surfaces that are contaminated Indirect contact Direct contact Foods that could be contaminated

22 Are all bacteria pathogens? No, most are harmless Some are even helpful –Examples of helpful bacteria: Lactobacillus: makes cheese, yogurt, & buttermilk and produces vitamins in your intestine Leuconostoc: makes pickles & sauerkraut Pediococcus: makes pepperoni, salami, & summer sausage USDA NIFSI Food Safety in the Classroom© University of Tennessee, Knoxville 2006

23 Tools and instruments in Microbiology lab Safety hoods are used to avoid splashing and inhaling possible pathogens. Agar plate for bacterial growth Slide used to make Bacterial smear And stain them Microscope to visualize the bacteria

24 Types of staining techniques Simple staining (use of a single stain) (use of a single stain) Differential staining (use of two contrasting stains (use of two contrasting stains separated by a decolorizing agent) For visualization of morphological shape & arrangement. shape & arrangement. Identification Visualization of structure Gramstain Acid fast stain stain SporestainCapsulestain

25 Gram Stain: It is the most important differential stain used in bacteriology because it classified bacteria into two major groups: a)Gram positive: Appears violet after Gram ’ s stain b) Gram negative: Appears red after Gram ’ s stain

26 Crystal violet ↓ Iodine ↓ Alcohol ↓ Safranin

27 Gram +ve S.aureus Gram –ve E.coli E.coli Step 1: Step 1: Crystal Violet Step 2: Gram ’ s Iodine Step 3: Decolorization (Aceton-Alcohol) (Aceton-Alcohol) Step 4: Safranin Red

28 Gram ’ s +ve Bacteria Gram ’ s -ve Bacteria

29 Gram-positive bacteria Have a thick peptidoglycan layer surrounds the cell. The stain gets trapped into this layer and the bacteria turned purple. Retain the color of the primary stain (crystal violet) after decolorization with alcohol Gram-negative bacteria have a thin peptidoglycan layer that does not retain crystal violet stain. Instead, it has a thick lipid layer which dissolved easily upon decoulorization with Aceton-Alcohol. Therefore, cells will be counterstained with safranin and turned red.

30 Types of culture media I.Based on their consistency a) solid medium b) liquid medium (ex: Blood culture) c) semi solid medium (for motility) -Some media are used for bacterial growth, some for Bacterial differentiation and others for bacterial selection. Macconkey agar which is selective for gram negative bacteria and differential them for lactose Fermentation.

31 Blood Culture Blood cultures are incubated and monitored electronically for bacterial and fungus growth.

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