Microbiology Lecture Notes PDF

Al-Maarif University College Department of Dentistry Medical Biology Lab Stage -1- Microbiology Lec. 8 Prepared by: Assistant Lec. Zaid Ahmad Hameed, MSc. Cancer...

Al-Maarif University College Department of Dentistry Medical Biology Lab Stage -1- Microbiology Lec. 8 Prepared by: Assistant Lec. Zaid Ahmad Hameed, MSc. Cancer Bio, BSc. Biology  Cell structure ( Bacterial Morphology and : Cell Physiology) structure All the cell is the basic functional and structural unit of life The cell plays a vital role in which perform bound organelles,-biological activities and include membrane individual functions to keep the cell alive and active.Twostructural types of cells are recognized: prokaryote and the eukaryote Prokaryotic cells have a simpler internal structure than eukaryotic cells, and they lacking membrane-enclosed.organelles prokaryot eukaryot e e The difference between Prokaryotic and Eukaryotic Cells  The branches of microbiology The different branches of microbiology are classified into pure and applied sciences which include: 1-Bacteriology 2-Mycology 3-Phycology 4 - Protozoology 5-Parasitology 6- Virology 7- Immunology Applied Microbiology Some of the most important branches of microbiology based on application include: 1) Food microbiology (is concerned with Research studies focus on a variety of microorganisms that contaminate/damage food and those that can be used for food processing and modification) 2) Medical Microbiology (is concerned with the diagnosis, prevention and treatment of diseases caused by different types of organisms (infection agents) 3) Industrial microbiology (is concerned with the use of given microorganisms for industrial production) 4) Agricultural microbiology (is concerned with microbes associated with plants and animal diseases and production)  Bacteriolog y What is Bacteriology? Bacteriology: is a branch of microbiology that is concerned with the study of bacteria and related aspects. Bacterial Characteristics: ▪ Bacteria are single-celled organisms. They lack organelles such as chloroplasts and mitochondria, and they do not have the true nucleus. So the bacteria is a typical example of prokaryote (karyote = nucleus) ▪ The bacterial genetic material is composedof a double strand of DNA that is continuous and circular, is located in a nucleoid, and it does not have a nuclear membrane. ▪ Bacteria also have a cell membrane and a cell wall that is often made of peptidoglycan. Together, the cell membrane and cell wall are referred to as the cell envelope. ▪ Reproduction: Bacteria reproduce asexually through binary fission, (one bacterial cell becomes two)  Classificatio ⎫ n Th e classification depends on the general structure of the bacteria. Classification Systems: 1) Bacterial size: The unit of measurement in bacteriology is micron (micrometer, μm), The size of pathogenic bacteria is (0.2 – 1.5 μm) in diameter (3 – 5 μm) in length. 2) Bacterial Morphology : Morphology and Gram staining are two of the most important systems when it comes to bacteria classification. With regards to morphology، Bacteria are classified into three major categories including Cocci (spherical in shape), Bacilli (rod-shaped), Spiral, and sometimes other shapes like Vibrio which is comma-shaped. Cocci – spherical / oval shaped major groups Bacilli – rod shaped Spirilla – rigid spiral forms Vibrios – comma shaped Spirochetes – flexible spiral forms Actinomycetes – branching filamentous bacteria Mycoplasmas – lack cell wall  (3Gram Stain According to the gram staining, the bacteria can classified in to two main types: Gram positive bacteria Gram negative bacteria  Bacterial Structure 1 Basic cell structure - found in all types of bacteria 2 Special cell structures - found in certain types of bacteria. − Basic structure Composed of the following structures: 1 Cell Wall 2 Cell membrane ( Cytoplasmic or Plasma membrane) Cell envelope composed from (cell wall & cell membrane) Functions of cell wall: 1- Protects the bacteria. 2- Allows them to live in “extreme” environments. 3- Give it their external shape The function of cell membrane: 1- Uptake of nutrients 2- Excretion of waste products In most bacteria the cell wall is made of bacterial starch (Peptidoglycan) and (Teichoic acid) 3- Secrets the enzymes 3- Internal structure of bacteria: - Cytoplasm - Ribosomes (for protein synthesis) - Mesosome (contributed with replications of bacterial cell) - Volutin granules (source of energy) 4- Genetic Material bacterial genes are contained on two kinds of DNA: chromosomal DNA (double strand of DNA) plasmids (composed of 100 copies of extra-chromosomal DNA) Genetic materials have the all genes and coding of bacterial feature and antibiotic resistance. Special cell structure: (Special structures – Additional structures) A- Pilli (fimbriae) Pilli are short, hair-like, protein: function “adherence” – stick to each other، stick to surfaces. Specialized “sex” pilus – conjugation( for genes exchanges) B- Flagella Flagella is an organ of motility (movement), so flagella below the types of bacteria according to the A = monotrichous B = amphitrichous C = lophotrichous D = peritrichous C- Capsule Some bacteria produce a capsule (a gelatinous, sticky layer) that allows bacteria to - Attach to substrates - Make “colonies” aggregate together - Increases pathogenic bacteria’s resistance to host’s immune defenses D- Slime layer loosely associated with the bacteria, that is help the bacterial cell to adherence with the surfaces of the tissues and cells. E-(bacterial spores) Endospores Some bacteria can form endospores to survive adverse conditions - Very resistant to destruction - Withstand desiccation and harsh conditions  Growth of bacterial cell Microbial growth involves an increase in the number of cells. Growth of most microorganisms occurs by the process of binary fission (one cell become two cells(  The Growth Curve Microorganisms show a characteristic growth pattern when inoculated into a fresh culture medium. The phases of 1- Lag phase (adaptation) growth curve are: 2- Log phase (experiential) 3- stationary phase (constant) 4- Decline phase (death)  Environmental Effects on Microbial Growth 1- Temperature : Is a major environmental factor controlling microbial growth. The cardinal temperatures are the minimum, optimum, and maximum temperatures at which each organism grows. So microorganisms can be grouped by the temperature ranges they require into: * Psychrophiles: Which prefer low temperature (0-15) * Mesophiles: Which prefer intermediate temperature (20-45) * Thermophiles: Which prefer low temperature (60 and above) 2- Oxygen: Based on Oxygen requirement, the bacteria classified as a follow: - Aerobic : which live only with the presence of oxygen -Anaerobic: which live only with absent of oxygen - Facultative anaerobic : live with or without oxygen. 3-Acidity (pH) Some organisms have evolved to grow best at low or high pH, but most organisms grow best between pH 6 and 8