lec 01. introduction to microbiology

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  • Introduction to Microbiology

    Sebghatullah Mansoor

    BS (Medical Sciences), MS (Microbiology), MPH (Continue)

    Medical faculty or Malalay University


  • Definition Microbiology is the study of microorganisms, a large and diverse

    group of microscopic organisms that exist as single cells or cell clusters;






    Environment effects

    Relationship with other organism or Human being


    The study of small organisms.



    Viruses, Viroids & Prions(not really organisms)


    Algae Fungi Protozoa

  • Microorganisms have a remarkable impact on all life and the physical and chemical makeup of our planet.

    They are responsible for cycling the chemical elements essential for life, including carbon, nitrogen, sulfur, hydrogen, and oxygen

    there are 100 million times as many bacteria in the oceans as there are stars in the known universe.

    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


  • At the beginning the bacteriology were termed for microbiology,

    By discovery of microscope (Robert Hookes Antonie van Leeuwenhoek), A hug evolution occurred in the history of medical science, specially in the microbiology science which by understanding other infectious agents such as Prions, Virus , Rickettsia , Fungus & Protozoa, the Bacteriology named were changed to Microbiology


  • Generally Microbiology is classified as follow;

    Medical Microbiology

    Industrial Microbiology

    Food Microbiology

    Soil Microbiology

    Marine Microbiology

    Plant Microbiology


  • Medical Microbiology Medical microbiology is a branch of medical science concerned with the

    prevention, diagnosis and treatment of infectious diseases. In addition, this field of science studies various clinical applications of microbes for the improvement of health, and classify as follow ;







  • Golden age of Microbiology

  • There are many methods to classify micro-organisms, which include;

    Binomial classification

    Classification according to Temperature

    Classification according to Gram staining

    Classification according to Presence of Oxygen

    Classification according to Morphology of bacteria

    Classification of Microorganisms (Taxonomy)

  • Classification of Microorganisms (Taxonomy)

    Binomial classification KINDOM the highest level in classification

    PHYLUM related classes

    CLASS related orders

    ORDER related families

    FAMILY related genera

    GENUS closely related species

    SPECIES organisms sharing a set of biological traits and reproducing only with their exact kind

    Further classifications especially with bacteria:

    Strainorganisms within a species varying in a given quality

    Typeorganisms within a species varying immunologically

  • Classification of Microorganisms (Taxonomy)Kingdom: Eubacteria

    Phylum: Proteobacteria

    Class: Gammaproteobacteria

    Order: Enterobacteriales

    Family: Enterobacteriaceae

    Genus: Escherichia

    Species: E. coli

    For example ;

    Escherichia coli

  • Classification according to Temperature Psychrophiles (Philic) ; Can survive under 15-25 C . e.g; Bacillus psychrophilus Mesophiles ; Can survive under 25-45 C . e.g; E.coli Thermophiles ; Can survive under 45-60 C . e.g ; Bacillus stearothermophilus

    Classification according to Gram Staining Gram Positive Bacteria, e.g; Staphylococcus aureus Gram Negative Bacteria, e.g ; E. coli

    Classification according to Presence of Oxygen Obligate aerobic; Which Oxygen is the primary needs. e,g; Mycobacterium tuberculosis Factitive anaerobic; Can survive with or without oxygen. e,g; E.coli Anaerobic; Which can not survive in the presence of Oxygen. e,g: Clostridium tetani Microaerophilic; Which need less amount of Oxygen. e,g ; Neisseria gonorrhea Aerotolerant; Do not required oxygen , nether dies in the presence of oxygen.

    e,g ; Lactobacillus

  • Classification according to Morphology

    Cocci ; Round shape , Diplo cocci ( two cocci), staphylococci ( cluster of cocci), Streptococci (chain of cocci)

    Bacilli ; Rod shape Vibrios ; Comma shape Spirilla ; Flexible spiral shape Spirochetes ; Spring type shape Actinomycetes ; Branching filamentous bacteria Mycoplasma ; Cell wall less bacteria

  • Classification according to Gram Staining

  • 1. Obligate aerobic2. Anaerobic3. Factitive anaerobic4. Microaerophilic5. Aerotolerant

    Classification according to Presence of Oxygen

  • Classification according to Morphology

  • Classification according to Morphology

  • Classification according to Morphology


  • Generally all organism are classified as follow

    Eukaryotes;-- Which has a true nucleus & all cellular organelles e,g: Fungi, Protozoa, Algae..

    Prokaryotes;-- Which has no true nucleus and missing some of cellular organelles e,g: Bacteria

    Viruses; -- Which is composed of Capsid or some have outer protein coating called envelop, and DNA or RNA not both. .e.g ; Polio virus, Hepatitis viruses

  • Virus

  • Characteristics of Prokaryotic and Eukaryotic Cells

  • Structure of bacteria Bacteria are classified by shape into three basic groups: cocci,

    bacilli, and spirochetes.

    The cocci are round, the bacilli are rods, and the spirochetes are spiral-shaped.

    Some bacteria are variable in shape and are said to be pleomorphic (many-shaped).

    The shape of a bacterium is determined by its rigid cell wall.

    The microscopic appearance of a bacterium is one of the most important criteria used in its identification.

  • A typical structure of bacteria

  • The major components of bacterial cells are;

    Cell wall

    Cytoplasmic membrane




    Structure of bacteria

  • Cell wall

    All bacteria have a cell wall composed of peptidoglycan except Mycoplasma,which are surrounded only by a cell membrane.

    The concept of gram positive & gram negative bacteria is based on bacterial cell wall which gram negative bacteria have a thin peptidoglycan covered by an outer lipid-containing membrane, whereas gram-positive bacteria have a thick peptidoglycan and no outer membrane.

    These differences explain why gram-negative bacteria lose the stain when exposed to a lipid solvent in the Gram stain process, whereas gram-positive bacteria retain the stain and remain purple.

    For better understanding we must to know about Gram staining method

    Structure of bacteria

  • Staining

    Micro-organism can not be seen by naked eyes, that why we must magnify the size of micro-organism For that reason we need a magnifier which is microscope which enlarges the organisms almost 1000 more than its actual size.

    The size of bacteria is measures by micron meter (m)

    The size of most bacteria rages from 1 to 3 m.

    The smallest bacteria is Mycoplasma 0.2 m, where as the largest is Borrelia 10 m

  • Most of the micro-organism are enable to seen even by microscope, we need to stain the organism

    According to PH all stains are acidic, alkali or neutral. Generally acidic materials are stains with alkali or in contrast alkali materials

    are stains with acidic . In general we classify the staining methods as follow. Simple staining Differential staining ( Gram staining) Acid fast staining Negative staining Flagella staining Capsule staining Spore staining


  • Simple staining

    in simple staining we use a single dye (methylene blue, carbol fuchsin, Safranin ) here just observe the shape of organism or bacteria either its cocci, rods or spirochetes


    1. Make a thin smear on a glass slide of a given sample

    2. Air dry it and cover with Methylene blue (CF, S)

    3. Wash with tap water and again air dry it

    4. Observe under the microscope , if the given sample is bacteria then we will see Bacilli or Cocci shapes of bacteria


  • Safranin stained bacilli Methylene Blue stained cocci

  • Differential staining (Gram Staining)

    Gram stain is the most important staining procedure which differentiate all the bacteria in two main categories either gram negative or gram positive bacteria. This method was discovered by Hans Christian Gram in Germany in 1884

    In this staining method we use more then one type of dye which include

    Crystal violet


    The mechanism of gram positive & gram negative bacteria is based on bacterial cell wall which gram negative bacteria have a thin peptidoglycan covered by an outer lipid-containing membrane, whereas gram-positive bacteria have a thick peptidoglycan and no outer membrane.


  • Gram positive Gram negative

  • Gram stain


    1. Make a smear of bacterial specimen on a glass slide

    2. Air dry it an cover with crystal violet for