MEDICAL MICROBIOLOGY MMIC 201 Prepared by Nabeel AlMawajdeh RN,MSC' King Saud UniversityAflaj Colleg

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MEDICAL MICROBIOLOGY (MMIC 201) Prepared by
Nabeel Al-Mawajdeh RN,MSC.King Saud
University-Aflaj College
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• CHAPTER 2
• Bacteriology
• Nabeel Al-Mawajdeh RN.MCS

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Bacteriology

• Bacteriology means the study of bacteria .
  Bacteria are prokaryotic cells (unicellular
  organisms with no a nucleus) with simple
  structures that typically range in size from
  about 0.5 to 20 micrometers.
• Nabeel Al-Mawajdeh RN.MCS

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Bacteria Characteristics

• The bacterium cell is a prokaryotic cell.
• Bacterium cell are very small (approximately
  0.1to 10.0 µm)
• Bacteria are widely distributed. It found in
  soil, air, water, and living bodies.
• Some bacteria cause diseases for animals and
  plants.
• Some bacteria live in our bodies as normal flora
  which harmless.
• Nabeel Al-Mawajdeh RN.MCS

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Normal Flora

• Normal flora Species of bacteria that colonize
  the human body and do not normally cause disease.
  Normal flora may cause some problems if it
  displaced or depleted because of using
  antibiotics. Organisms of the normal flora are
  normally found on surface tissues (i.e., the
  skin, mucous membranes, the gastrointestinal
  system, and vagina).
• Nabeel Al-Mawajdeh RN.MCS

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Functions of Normal Flora

• They perform important metabolic functions e.g.
• a. Synthesis of vit. K.
• b. Conversion of bile pigments and bile
  acids.
• c. Absorption of nutrients from the
  intestine.
• They inhibit colonization and infection by
  pathogenic bacteria as they
• a. Interfere with bacterial adherence.
• b. Maintain inhibitory PH in vagina and
  skin.
• c. Compete for essential nutrients.
• d. Produce inhibitory substances e.g. fatty
  acids and
• colicins.
• Nabeel Al-Mawajdeh RN.MCS

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Prokaryotic

• Prokaryotic cells characteristics
• They lacks the nuclear envelope so there is no
  nucleus.
• There is no nucleolus.
• Have simple enzyme system and lack most of the
  cellular organelles like mitochondria.
• Reproduce by binary fission (simple dividing
  process)
• Found in bacteria ad Cyanobacteria.
• Nabeel Al-Mawajdeh RN.MCS

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Eukaryotic

• Eukaryotic cells characteristics
• Have nuclear envelope and cellular organelles.
• Have nucleolus.
• Have complex enzyme system.
• Reproduce by simple and complex processes.
• All the living cells are eukaryotic cells except
  that of bacteria.
• Nabeel Al-Mawajdeh RN.MCS

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Bacterial Structure
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Bacteria Structure

• Cell envelope
• Cell membrane (plasma membrane)
• It is a semi permeable membrane that
  surrounds the cytoplasm of all bacterial cells,
  it composed of two layers of phospholipids,
  proteins, and carbohydrate. Its main function is
  to maintain a constant environment within the
  interior of the cell by controlling the transport
  mechanism between the cell and the surrounding
  medium.
• Nabeel Al-Mawajdeh RN.MCS

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Bacteria Structure (Contd)

• Cell wall
• A structure surrounding the cell, composed
  of Peptidoglycan (polysaccharides and proteins).
  Peptidoglycanis responsible for the rigidity of
  the bacterial cell wall and for the determination
  of cell shape. There are two main types of
  bacterial cell walls, Gram positive and Gram
  negative, which are differentiated by their Gram
  staining characteristics.
• Nabeel Al-Mawajdeh RN.MCS

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Bacteria Structure (Contd)

• Capsule
• It is a gelatinous layer outside the cell
  wall of some species. It is composed of
  polysaccharides. It increase the Pathogenicity of
  bacteria because capsulated
• bacteria are not easy to be destroyed by
  host cell. Capsules are not usually stained by
  gram stain.
• Flagella
• Flagellum is an appendage of the cell
  membrane that helps in bacterial movement, and
  can play a role in the production of disease. It
  is composed of a single protein called flagellin.
• Nabeel Al-Mawajdeh RN.MCS

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Bacteria Structure (Contd)

• Pili (synonym fimbriae)These are hair like
  filaments that extend from the cell surface.
  They are shorter and thinner that flagella and
  composed of a protein called pilin. They are
  found mainly on gram negative bacteria. They help
  bacteria to adhere together and to the surface of
  host cell.
• Nabeel Al-Mawajdeh RN.MCS

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Bacteria Structure (Contd)

• Intracellular Structures
• Cytoplasm
• Which is a fluid that fills the cell. The
  ribosome and other internal structures are
  impeded in cytoplasm. All the internal
  biochemical activities are occur within it.
• Nuclear material
• Electron microscope showed that the
  bacterial genetic material is composed of a
  bundle of a double stranded DNA molecule
  (chromosome) that not surrounds by a nuclear
  membrane.
• The chromosome carries the genetic
  information and it duplicates before cell
  division.
• Nabeel Al-Mawajdeh RN.MCS

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Bacteria Structure (Contd)

• Plasmids
• These are extra chromosomal double
  stranded circular DNA that are capable of
  replicating independent of the bacterial
  chromosome. It helps bacteria to resist
  antibiotics.
• Nabeel Al-Mawajdeh RN.MCS

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Bacteria Structure (Contd)

• Ribosomes
• Ribosome is cellular organelle that found
  is in cytoplasm. Its function is to synthesize
  proteins
• for the bacterial cell.
• Inclusion granules
• They are found in cytoplasm. They serve as
  energy and nutrient reservoirs. They may be rich
  in lipids and carbohydrates.
• Nabeel Al-Mawajdeh RN.MCS

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Bacteria Structure (Contd)

• Endospores
• These are small thick walls formed in the
  cytoplasm that helps to resist the unfavorite
  environmental conditions like depletion of
  nutrients, heat, and dryness. The spores
  formation occurs by the development of an
  ingrowth of the cytoplasmic membrane cutting off
  a portion if the cytoplasm. Then a thick cortex
  and a tough spore coat are formed.
• Endospores Spores are commonly found in
  the genera Bacillus and Clostridium.
• Nabeel Al-Mawajdeh RN.MCS

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Bacteria Shapes

• There are three basic shapes
• Coccus An average coccus is about 0.5-1.0
  micrometer (µm) in diameter.
• Rod or bacillus An average bacillus is 0.5-1.0
  µm wide by 1.0-4.0 µm long.
• Spiral Spirals range in size from 1 µm to over
  100 µm in length.
• Nabeel Al-Mawajdeh RN.MCS

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Bacteria Shapes

• Spiral

• Coccus

• Rod

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Gram Reactions

• Gram-positive
• Gram-positive bacteria have a relatively
  thick layer of Peptidoglycan and can retain a
  crystal violet-iodine complex when treated with
  acetone or alcohol, and appear blue-black or
  purple when stained using Gram's method.
• Nabeel Al-Mawajdeh RN.MCS

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A Gram-positive cell
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Gram Reactions (Contd)

• Gram-negative
• Gram-negative bacteria have a thin layer
  of Peptidoglycan and cannot retain the crystal
  violet-iodine complex.
• Nabeel Al-Mawajdeh RN.MCS

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A Gram-negative cell
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Basic Nutritional Requirements

• Oxygen Requirements 
• Obligate aerobe Bacteria grow only on the
  presence of O2.
• Microaerophilic These bacteria will grow in low
  
• oxygen concentrations.
• Obligate anaerobe Grow in the absence of free
  O2.
• Facultative anaerobes Grow in the presence or
  absence of O2.
• Nabeel Al-Mawajdeh RN.MCS

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Nutritional Requirements (contd)

• Nutrient Requirements
• - Autotrophs Obtain carob and/or sugar from
  sunlight or chemical reactions.
• - Heterotrophs Obtain carob and/or sugar
  from the
• environment.
• Nabeel Al-Mawajdeh RN.MCS

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Nutritional Requirements (contd)

• Temperature
• According to the optimal temperature,
  bacteria are classified into 3 groups
• Psychrophiles These live in low temperature
• (lt 20C)
• Mesophiles These live in moderate
  temperature(20-40C)
• Thermophiles These live in high temperature (gt
  45C)
• Nabeel Al-Mawajdeh RN.MCS

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Nutritional Requirements (contd)

• PH
• Most bacteria grow at narrow range of PH
  (7.2- 7.6).
• Acidophiles are bacteria that grow optimally
  under acidic conditions (pH lt 7.0)
• Alkaphiles prefer alkaline or basic conditions
  (pH gt 7.0).
• Nabeel Al-Mawajdeh RN.MCS

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Bacteria, Growth Reproduction

• Bacteria grow and replicate in a process known
  as binary fission.
• The typical Bacterial Growth Curve includes 4
  phases
• 1. Lag phase It is the first phase during which
  no cell division occurs. Bacterial cells adapt to
  the new environment so they dont divide but they
  are metabolically active.
• 2. Logarithmic phase After the cells adjusted to
  the new environment, rapid cell division occurs
  and the number of the cells increase steadily by
  the time.
• 3. Stationary phase The growth rate slows as
  nutrients become exhausted and waste products
  accumulate. The rate of the bacterial growth
  equals the rate of bacterial death. The number of
  bacterial cells remains constant.
• 4. Decline phase(Death phase) Bacteria run out
  of nutrients and die.
• Nabeel Al-Mawajdeh RN.MCS

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Bacterial Growth Curve
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Binary Fission

• Binary fission is the process by which a bacteria
• grow and replicate.
• Bacteria can exchange genetic materials via
  conjugation.
• Nabeel Al-Mawajdeh RN.MCS

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Binary Fission (Contd)

• Stages of binary fission
• The bacterial chromosome attaches to the cell
  membrane.
• The chromosome duplicates.
• The 2 copies of the chromosome still attach to
  the cell membrane.
• The bacterial cell begins narrowing at the
  middle.
• The narrowing continue until the cell divides
  into two new cells.
• Nabeel Al-Mawajdeh RN.MCS

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Binary Fission
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Common Bacterial Infections

• Staphylococcus a gram-positive bacteria .
• - S. aureus e.g. food poisoning, impetigo,
  and furuncles (boils).
• - S. epidermidis. e.g. endocarditis.
• Streptococcus. a gram-positive bacteria.
• e.g. Pharyngitis, scarlet fever, and
  rheumatic fever.
• - S. pneumonia is a common cause of bacterial
  pneumonia and meningitis.
• Neisseria.
• - N. gonorrhoea is the causative agent of
  gonorrhoea.
• - N. meningitides is a leading cause of adult
  meningitis.
• Nabeel Al-Mawajdeh RN.MCS

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Common Bacterial Infections (Contd)

• Escherichia. E. coli. e. g. gastroenteritis, UTIs
  and neonatal meningitis.
• Salmonella. E.g. enteritis.
• - S. typhi . e, g. typhoid fever.
• Vibrio.
• - V. cholera. E.g. cholera.
• Clostridium.
• - C. tetani e.g. tetanus (lockjaw)
• Nabeel Al-Mawajdeh RN.MCS

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• The End
• Nabeel Al-Mawajdeh RN.MCS