top of page

Aerobic vs. Anaerobic Bacteria

During the breakdown of oxygen, several highly reactive molecules are formed such as hydrogen peroxide and superoxide free radical. These have the potential to harm/kill the bacteria. In fact, macrophages and neutrophils utilize this very mechanism to kill any bacteria they gobble up (phagocytose), As a defense mechanism, bacteria have acquired/possess various enzymes to break down these toxic oxygen compounds. These enzymes are the catalase, peroxidase & superoxide dismutase enzymes (see reaction below). 
Whether a bacteria can survive in the presence of oxygen depends on how many of these enzymes are present. Study the chart below to learn more about the growth characteristics of each organism in the presence of oxygen.

  • Staphylococcus

  • Bacillus anthracis

  • Corynebacterium

  • Listeria

  • Actinomyces

OBLIGATE aerobES
OBLIGATE ANAEROBES
facultative aerobES
MICROAEROPHILIC
  • Require oxygen for growth.
  • These organisms use glycolysis, the Krebs TCA cycle and electron transport chain with oxygen as the final electron acceptor.
  • Possess all 3 enzymes:
    • Catalase
    • Peroxidase
    • Superoxide dismutase
  • Prefers oxygen for growth, but can grow without oxygen by using fermentation for energy.
  • Possess 2 enzymes:
    • Catalase​
    • Superoxide dismutase
  • Also called "Aero-tolerant" anaerobes
  • Requires reduced oxygen concentration for growth.
  • Use fermentation for energy
  • Have no electron transport system
  • Have 1 enzyme:
    • Superoxide dismutase​
  • CANNOT grow in the presence of oxygen.
  • Lacks all 3 enzymes required for oxygen breakdown.

  • Nocardia (partially acid fast)

  • Bacillus cereus

  • Streptococcus

  • Clostridium

  • Neisseria

  • Pseudomonas

  • Bordetella

  • Legionella

  • Brucella

  • Most other gram negative rods

  • Spirochetes

    • Treponema​

    • Borrelia

    • Leptospira

  • Campylobacter​

  • Bacteroides

  • Mycobacterium (acid fast)

  • Mycoplasma (no cell wall)

Gram POS

Gram NEG

OTHER

HIGHEST
OXYGEN
CONC.
LOWEST
OXYGEN
CONC.

AEROBIC BACTERIA

Gram POS Organisms

Rods/Bacilli

Cocci

  • Arcanobacterium

  • Bacillus

  • Corynebacterium

  • Erysipelothrix

  • Gardnerella

  • Lactobacillus

  • Listeria

  • Mycobacterium (other than M. tuberculosis)

  • Nocardia

  • Bartonella

  • Bordetella

  • Brucella

  • Campylobacter

  • Eikenella

  • Franciscella

  • Haemophilus

  • Helicobacter Kingella

  • Moraxella

  • Neisseria

  • ENTEROBACTERIACAE

    • Citrobacter

    • Edwardsiella

    • Enterobacter

    • Escherichia

    • Hafnia

    • Klebsiella

    • Morganella

    • Proteus

    • Providencia

    • Salmonella

    • Serratia

    • Shigella

    • Yersinia

  • NON-ENTEROBACTERIACAE

    • FERMENTATIVE

      • Aeromonas

      • Pasteurella

      • Plesiomonas

      • Vibrio

    • NON-FERMENTATIVE

      • Acinetobacter

      • Alcaligenes

      • Burkholderia

      • Flavobacterium

      • Pseudomonas

      • Stenotrophomonas​​

Coccobacilli

Cocci

Rods/Bacilli

Cocci

Rods/Bacilli

Cocci

Rods/Bacilli

Gram NEG Organisms 

  • Staphylococcus

  • Streptococcus

ANAEROBIC ORGANISMS

Gram POS Organisms

Rods/Bacilli

Rods/Bacilli

Cocci

Cocci

Cocci

  • Actinomyces

  • Bifidobacterium

  • Clostridium

  • Eubacterium

  • Propionibacterium

  • Peptococcus

  • Peptostreptococcus

  • Bacteroides

  • Fusobacterium

  • Porphyromonas

  • Prevotella

  • Veillonella

Gram NEG Organisms 

Rods/Bacilli

Rods/Bacilli

Unstainable Organisms

No Cell Wall

Spirochetes

Obligate Intracellular

Other

  • Mycoplasma

  • Ureaplasma

  • Borrelia

  • Leptospira

  • Spirillum

  • Treponema

    • ​Can't be seen with light microscope

  • Anaplasma

  • Chlamydia

  • Chlamydophila

  • Coxiella

  • Ehrlichia

  • Orientia

  • Rickettsia

  • Legionella (weakly gram neg rod- requires silver stain)

  • Mycobacterium tuberculosis

MICRO & IMMUNO

NEXT TOPIC

Lab workup: Gram Pos Cocci

PREVIOUS TOPIC

Bacteria Morphology

 

Next up, we will learn more about the laboratory workup of the various organisms.

 

Let's start with how to distinguish between the gram-positive cocci-

Staphylococcus vs. Streptococcus

bottom of page