Bacteria
Bacteria are the earliest and most ubiquitous life forms on Earth. These organisms have an impact on almost all others, either positively or negatively. Bacteria have a major impact on the global carbon balance of the Earth, and they are the only organisms to convert gaseous nitrogen to a solid form. Some are able to decompose toxic substances, others have been found that can degrade plastic. There are many known plant and animal diseases caused by bacteria, and the chloroplast and mitochondria found in eukaryotic cells have their origin with bacteria. Humans use bacteria to create many drugs, as well as cheese and yogurt.
Features
Prokaryotes: no nucleus or large organelles (except ribosomes)
Nucleoid: circular DNA (chromosome)
Microscopic, single-cell organisms usually ~2 micrometers in length, with some of the largest specimens reaching 750 micrometers
Both heterotrophic and autotrophic forms
Multiply through binary fission, and not sexual reproduction
Pilus: connects organisms; allows conjugation
Cell wall: complex suite of molecules
Flagella: allows motility
Forms
Spherical-shaped
Rod-shaped
Spiral-shaped
Symbiotic Interactions
Plants
Most blights, soft rots, and wilts are bacterial
Nitrogen fixation
Animals
Tuberculosis, cholera, anthrax, gonorrhea, whooping cough, typhoid, botulism, syphilis, diphtheria, tetanus
Crucial to digestion
Ecological Importance
Major impact on global carbon balance
Cyanobacteria are only organisms able to “fix” free nitrogen into usable form (nitrate or nitrite)
Nitrate/nitrite can form through physical processes, such as lightning, but at a fraction of the ability of cyanobacteria
Decompose toxic substances, natural & artificial
Commercial uses
Many drugs and antibiotics (target living organisms, not viruses)
Used to create cheese and yogurt
Geologic Age
Appear during Paleoarchean (3.60–3.20 billion years)
Questions for thought
What are bacteria?
What is a prokaryote?
What unique role do bacteria play in the environment?
How are they important for horticulturists?
Additional Reading
Nova Next - What is a Healthy Microbiome?