Bacterial Classification

• Analysis of 16S rRNA sequences has yielded a universal

  evolutionary
• Microorganism: A microscopic organism may exist in its single-celled form or in a colony of cells, can not seen by naked eyes
• Giant bacteria: thiomergarita niambiensis, 100 to 200 times larger than average bacteria
• Classification systems in prokaryotes:

  • Phenotypic classification

  – Morphological

  – Anatomical

  – Staining

  – Cultural characteristics

  – Nutrition

  – Environmental factors

  – Biochemical reactions

  – Antigenic structure

  • Genotypic classification

  – DNA-DNA hybridization

  – G+C content
• Bacterial Shapes: Coccus, Bacillus, Spirillum
• Cocci: spherical, single-celled bacteria`
• Bacilli: rod-shaped bacteria
• Spirilla: spiral shaped bacteria
• cocci

  A) coccus

  B) diplococci

  C) staphylococci

  D) streptococci

  
• bacillus

  A) coccobacillus

  B) diplobacilli

  C) palisades

  D) streptobacilli

  
• spirilla

  A) vibrio

  B) spirilla

  C) spirochetes

  
• Filamentous Bacteria

  • very long thin filament-shaped bacteria. Some of them form

  branching filaments resulting in a network of filaments called

  ‘mycelium’.
• Other bacteria types:

  • Star Shaped Bacteria
  • Rectangular Bacteria
  • Pleomorphic Bacteria

  – Lack rigid cell wall

  – Highly pleomorphic and indefinite shape
• Classification Based on Anatomical Features:

  • Capsule

  – Capsulate

  – Non-capsulate

  • Flagella

  – Flagellate

  – Aflagellate

  • Fimbriae and Pili
  • Spore

  – Spore-forming

  – Non-sporing
• Capsule or Slime layer(Glycocalyx)

  Definition:

  • A thick layer of slimy material secreted by the bacteria on their surfaces

  Function:

  • Help the bacteria to attach onto the host cells they are

  infecting

  • Protect the bacteria from immune cells such as phagocytes
• flagella: long, thin, threads of proteins that allow bacteria to move, number and arrangement varies
• pili (fimbriae): short, hair-like structures that attach bacteria to surfaces (adhesion)

  sex pilus: aids in transfer of genetic information from one plasmid to another
• ....

  A) fimbriae

  B) pili

  C) flagella

  D) plasmid

  
• pili are only found in gram negative bacteria and are only for genetic material exchange but fimbriae are in gram negative and positive bacteria and are use for cell to surface attatchement
• Endospore: When the environmental conditions do not support growth some

  bacteria turn into an inactive but very resistant form called spore.

  • To turn into spore the cell looses most of its water content and it is

  surrounded by a thick wall.

  • Spores are resistant to;

  – ultraviolet,

  – gamma radiations,

  – drying,

  – high temperature (boiling),

  – starvation ,

  – many disinfectants.
• ...

  A) sporulation

  
• Classification based on staining reaction:

  • Gram’s Stain

  – Gram-positive cocci

  – Gram-negative cocci

  – Gram-positive rods

  – Gram-negative rods

  • Acid Fast Stain

  – Acid fast bacilli

  – Non-acid fast bacilli
• Classification based on cultural characteristics:

  • Extra growth factors requirements

  – Fastidious

  • any organism that has a complex nutritional requirement

  – Non-fastidious

  • Hemolysis on sheep blood agar

  • Alpha hemolysis

  • Beta-hemolysis

  • Gamma-hemolysis

  • Utilization of carbohydrates

  • Oxidative

  • fermentative

  • Growth rate

  – Rapid growers (ex; 24 hours)

  – Slow growers (ex; 26 days)

  
  

  • Pigment production

  – Pigment producer

  – Pigment non-producer
• Classification Based on Nutrition:

  • Autotrophs

  – obtain their nutrition from inorganic compounds.

  – Carbon dioxide is typically the sole source of cellular carbon

  • Heterotrophs

  – require organic sources of carbon

  • Phototrophs

  – absorb light energy, then utilize this in photosynthesis to create cellular energy

  • Chemotrophs

  – obtain chemical energy from their surroundings and convert it into adenosine triphosphate (ATP) for cellular use.

  • Lithotrophs

  – use reduced inorganic compounds as the electron donor (Hdonor)in anaerobic or aerobic respiration.
• Classification Based on Environmental Factors

  • Temperature

  • Oxygen dependence

  • pH

  • Salt concentration
• • Most bacteria are mesophilic.

  • Mesophilic bacteria grow best at 30-37°C.

  • Optimum temperature for growth of common pathogenic bacteria is 37°C.
• • Psychrophiles :

  • Cold lovers

  • Range (15-20 ˚C )

  • Mesophiles

  • Range (30-37 ˚C )

  • Thermophiles

  • Heat lovers

  • Range(50-60 ˚C )

  • Extremely thermophiles

  • Range (as high as 250 ˚C )
• ....

  A) obligate anaerobes

  B) obligate aerobes

  C) aerotolerant anaerobes

  D) microaerophiles

  E) faculative anaerobes

  
• ...

  A) obligate aerobes

  B) obligate anaerobes

  C) faculative anaerobes

  D) aerotolerant anaerobes

  E) microaerophiles

  
• Most bacteria grow between pH 6.5-7.5 but there are also:

  • Acidophiles

  • Alkaliphiles

  • Neutrophiles
• Halophiles

  – require at least some salt (NaCl) for their growth

  Non-halophiles

  – Do not need salt for growing
• ....

  A) Staining with Methylene Blue

  B) capsule stains

  C) flagella stains

  D) endospore stains

  E) gram stain

  F) acid fast stain

  
• Chemical fixation;Alcohol

  physical fixation ; Heat
• Simple Staining

  • Determine shape and morphological arrangement
• Gram Staining: READ IMAGE

  
• Peptidoglycan Layer

  • The “glycan” part consists of alternating units of N-acetylglucosamine (NAG) and N- acetylmuramic acid (NAM), which is located immediately outside of the cytoplasmic membrane.

  • The “peptido” part consist of a short string of amino acids. It cross-links the adjacent polysaccharide strands at the NAM subunit.

  
• .....

  A) positive

  B) negative

  
• Gram Staining: READ

  A) positive

  B) negative

  
• LONG PPT

  • Lipopolysaccharide
  • Outer membrane
  • Negative
  • Gram
  • Positive
  • Peptodiglycan (thick)
  • Teichonic acid

  
• Acid- Fast staining

  • Acid fast cells contain a large amount of lipids and waxes on

  their cell walls like mycolic acid