Question

What does it mean for an organism to be anaerobic?

Answer 1

Anaerobic bacteria may be unicellular or multicellular organisms.
Anaerobic bacteria use fermentative pathways like propionic acid fermentation and butyric acid fermentation.

Complete answer:
An anaerobic organism is an organism that does not require oxygen for sustenance. Anaerobic organisms react negatively when they come in contact with oxygen. Oxygen might prove to be fatal for some anaerobic organisms.
Anaerobic organisms are divided into three categories. They are:
- Obligate anaerobes
- Aerotolerant anaerobes
- Facultative anaerobes
Obligate anaerobes are anaerobic organisms that are harmed in the presence of oxygen. Bacteria that live near hydrothermal vents near the deep seafloor are examples of obligate anaerobes.
Aerotolerant anaerobes are anaerobic organisms that can tolerate the presence of oxygen but do not derive any sustenance from oxygen. Propionibacterium acnes is an example of aerotolerant anaerobic bacteria.
Facultative anaerobes are anaerobic organisms that can propagate in the presence and absence of oxygen. They can survive with and without oxygen. Escherichia coli is an example of facultative anaerobic bacteria.
Anaerobic organisms use various methods for metabolism. Obligate anaerobic organisms use both fermentation and anaerobic respiration. All aerotolerant anaerobic organisms use fermentation for carrying out metabolic processes. Facultative anaerobic organisms utilize aerobic respiration in the presence of oxygen. Some facultative anaerobic organisms use fermentation or anaerobic respiration in the absence of oxygen.

Note:
Culturing anaerobic bacteria becomes a problematic process as normal bacterial culturing occurs in oxygen-rich environments.
Martinus Beijerinck, in 1913 identified Clostridium butyricum as an anaerobic bacterium. Deep sea surfaces are common anaerobic environments.