Introduction to microbiology

Transcription

1 Sulaimani University College of Pharmacy Microbiology Introduction to microbiology Dr. Abdullah Ahmed Hama PhD. Molecular Medical Parasitology 1

2 Definition Microbiology: is the study of microorganisms, 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. Humans have an intimate relationship with microorganisms; more than 90% of the cells in our bodies are microbes. The bacteria present in the average human gut weigh about 1 kg, and a human adult will excrete his or her own weight in fecal bacteria each year. Medical microbiology : is the study of causative agents of infectious diseases of humans and their reactions to such infections; it also deals with etiology, pathogenesis, laboratory diagnosis, specific treatment and control of infection (immunization). 2

3 Bacteriology: the science of bacteria, the causative agents of a member of infectious diseases. Virology : the science of viruses, non-cellular living systems, capable of causing infectious diseases in man. Immunology: the science which concerned with mechanisms of body protection against pathogenic microorganisms and foreign cells and substances. Mycology: the study of fungi pathogenic for man. Protozoology : which deals with pathogenic unicellular animal organisms. 3

4 Classification of Microorganisms Protista Vira DNA-viruses and RNA-viruses Eukaryotes Fungi Algae Protozoa Slime molds Prokaryotes Blue-green algae Bacteria

5 Bacteria: is a Group of organisms unique among living things. Age fossil record to 3.5 billion years. Size typically less than 2 µm in length. Simple Internal cellular arrangement. Unique cellular components (Cell walls, amino acids, chemical components).

6 Development of Microbiology A brief history Two events really shape the development of microbiology o Development of the microscope ( ) o Controversy over spontaneous generation ( ) Microscopy First microscopic observations were by Robert Hooke and Antonie van Leeuwenhoek Pasteur ( ) 6

7 Germ Theory Soon after the end of spontaneous generation (SG), there was expanded interest in microbes as causative agents of disease. A very difficult problem since it is difficult to determine if microbes present in a diseased person or animal were the cause or the result. Rober Koch (1876) Working with anthrax demonstrated o Microbe always associated with the disease o Disease was always transferred with blood transfer This led to a series of postulates to demonstrate the germ theory o Disease must be present o Organism isolated and grown in pure culture o Cause the disease if re-introduced to a host o Organism must be recovered from the now diseased host.

8 Morphology and shape of Bacteria Shape of Bacteria Depending on their shape, bacteria are classified into several shape: 1. Cocci: Cocci (from kokkos meaning berry) are spherical, E.coli, Salmonella, Shigella. 2. Bacilli: Bacilli (from baculus meaning rod) are relatively straight, rod shaped (cylindrical) cells (B.anthracis, C.tetani, C.botuli-num). 3. Vibrios: Vibrios are curved or comma-shaped rods and derive the name from their characteristic vibratory motility. 4. Spirilla: Spirilla are rigid spiral or helical forms. 5. Spirochetes: Spirochetes (from speira meaning coil and chaite meaning hair) are flexuous spiral forms. 6. Mycoplasma: Mycoplasma are cell wall deficient bacteria and hence do not possess a stable morphology.

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10 ARRANGEMENT OF ROD-SHAPED BACTERIA

11 SPIRAL FORMS Vibrios are cells, which resemble a comma in appearance (curved rods). Typical representative of this group is Vibrio cholerae. Spirilla Helicobacter pylori: causative agent of ulcer disease of stomach.

12 3. Spirochaetes are flexuous spiral forms which include: Treponema (T.pallidum) (1), Borrelia (B.recurrentis) (2), Leptospira (L.interrogans) (3) 1 2 3

13 Bacterial characteristic continue

14 Cell wall G -ve & G +ve The tasks of the complex bacterial cell wall are to protect the protoplasts from external environment. to withstand and maintain the osmotic pressure gradient between the cell interior and the extracellular environment (with internal pressures as high as kpa), to give the cell its outer form and to facilitate communication with its surroundings. Murein (peptidoglycan):the most important structural element of the wall is murein, a netlike polymer material surrounding the entire cell. It is made up of polysaccharide chains cross linked by peptides

15 Bacterial structural The cell wall of Gram-positive bacteria (Fig. 3.10). The murein succubus may consist of as many as 40 layers (15 80 nm thick) and account for as much as The cell wall of Gram-positive bacteria (Fig. 3.10). The murein succubus may consist of as many as 40 layers (15 80 nm thick) and account for as much as30% of the dry mass of the cell wall. The membrane lipoteichoic acids are anchored in the cytoplasmic membrane, whereas the cell wall teichoic acids are covalently coupled to the murein. The physiological role of the teichoic

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17 The cell wall of Gram-negative bacteria. Here, the murine is only about 2 nm thick and contributes up to 10% of the dry cell wall mass. The outer membrane is the salient structural element. It contains numerous proteins (50% by mass) as well as the medically critical lipopolysaccharide.