DOMAIN BACTERIA

PHENOTYPIC CATEGORIES
- - Gram negative with cell walls
  - Gram positive with cell walls
  - Bacteria without cell walls

CELL WALL DEFICIENT BACTERIA

These are bacteria which lose their cell walls during adverse growth conditions but revert to their original shape when placed in favorable growth conditions.
L-forms ( Lister institute )
Result from:
- - Spontaneous mutation
  - Effects of chemicals ( penicillin)

MYCOPLASMA

These are bacteria lack cell walls thus appear in various shapes – PLEOMORPHIC
Mycoplasma pneumoniae

All cocci are gram positive except :
- - Neisseria
  - Veillonella
  - Branhamella

All bacilli are gram negative except:
- - Corynebacterium
  - Clostridium
  - Bacillus
  - Mycobacterium

STAINING

Because bacteria are colorless and transparent they are usually stained to give color to the organisms so that it will be easier to view them under the microscope.

PREPARATION FOR STAINING

PURPOSES OF FIXATION

- - to kill microorganisms
  - to preserve the morphology of bacteria
  - to anchor the smear to the slide

TYPES OF STAINING

SIMPLE STAINING
- Simple staining is used to determine cell shape, size, and arrangement. It uses only one kind of stain.

DIFFERENTIAL STAINING
- Differential staining methods usually require more than one stain. These procedures permit the differentiation of cell types or cell structures.
  - - - Gram staining
      - Acid fast staining
SPECIAL STAINING (STRUCTURAL STAINING)
- Special staining procedures are done to observe capsules , spores and flagella.

GRAM STAINING

The Gram stain procedure which was developed by Dr. Hans Christian Gram in 1883, distinguishes between Gram positive and Gram negative groups by coloring these cells red or violet.
Gram positive bacteria stain violet due to the presence of a thick layer of peptidoglycan in their cell walls, which retains the crystal violet these cells are stained with. Gram negative bacteria stain red, which is attributed to a thinner peptidoglycan wall, which does not retain the crystal violet during the decoloring process.

GRAM VARIABLE BACTERIA

ACID FAST BACTERIA

STRUCTURAL STAINING PROCEDURES

CAPSULE STAINS
- Capsule stain is a type of differential stain which uses acidic and basic dyes to stain background & bacterial cells respectively so that presence of capsule is easily visualized.
- The India ink method uses the dyes, crystal violet and india ink (nigrosin). The capsule is seen as a clear halo around the microorganism against the black background. This method is used for demonstrating Cryptococcus.
FLAGELLA STAINS
ENDOSPORE STAINS

ATMOSPHERIC REQUIREMENTS

AEROBES utilize molecular oxygen for energy.
OBLIGATE AEROBES require an atmosphere containing 20-21% O2.
- - Mycobacteria, fungi
MICROAEROPHILES require lower concentrations of O2 (5%).
- - Neisseria gonorrheae
  - Campylobacter spp.

ANAEROBES do not require O2 for life and reproduction.
OBLIGATE ANAEROBES can only grow in an anaerobic environment.
AEROTOLERANT ANAEROBES grow better in the absence of O2 but can survive in its presence.
FACULTATIVE ANAEROBES can survive in the presence or absence of oxygen.
- - Enterobacteriaceae
  - Streptococci
  - staphylococci

UNIQUE OR RUDIMENTARY BACTERIA

RICKETTSIA
- The rickettsiae are a diverse collection of obligately intracellular Gram-negative, non-sporeforming highly pleomorphic bacteria found in ticks, lice, fleas, mites, chiggers, and mammals.
- These bacteria cause arthropod borne diseases such as Rocky Mountain Spotted Fever.
CHLAMYDIAS
- Chlamydias are obligate intracellular pathogens transmitted by inhalation of aerosols or by direct contact between hosts.
- They are referred to as energy parasites because they can produce ATP's.
- Chlamydia trachomatis is one of the most common causes of sexually transmitted urethritis.
MYCOPLASMAS
- Mycoplasmas are the smallest of the cellular microbes.
- Mycoplasmas lack cell walls thus are pleomorphic.
- They cause atypical pneumonia and genitourinary infections
- They produce fried egg shaped colonies when cultured.

PHOTOSYNTHETIC BACTERIA

ARCHAEA

These are “ancient” microorganisms that are able to live in extreme environment.
They possess cell walls without peptidoglycan.

REFERENCE:

Engelkirk, P. G. (2018). Burton's microbiology for the health sciences 11th ed.(ch 1). Philadelphia: Lippincott Williams & Wilkins.