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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
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
Thiomargarita magnifica, is a megabacterium found in the Caribbean mangroves that can reach up to 2 cm (Volland et al. 2022)!
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
Above: Thiomargarita magnifica, is a megabacterium can reach up to 2 cm (Volland et al. 2022)
Forms
Forms
Spherical-shaped
Rod-shaped
Spiral-shaped
Symbiotic Interactions
Symbiotic Interactions
Plants
Plants
Most blights, soft rots, and wilts are bacterial
Nitrogen fixation
Animals
Animals
Tuberculosis, cholera, anthrax, gonorrhea, whooping cough, typhoid, botulism, syphilis, diphtheria, tetanus
Crucial to digestion
Ecological Importance
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
Commercial uses
Many drugs and antibiotics (target living organisms, not viruses)
Used to create cheese and yogurt
Geologic Age
Geologic Age
Appear during Paleoarchean (3.60–3.20 billion years)
Questions for thought
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
Additional Reading
Genomes uncover the extraordinary drive to survive in microbes beneath Antarctic ice (Phys.org 10Sep2025)
└Kim et al. (2025) Genetic isolation and metabolic complexity of an Antarctic subglacial microbiome
Desert bacterium shows promise in combating crop fungi and boosting plant growth (Phys.org 27Aug2025)
└Mohamad et al. (2025) Dual-functionality of Nocardiopsis alba B57 in biocontrol and plant growth: a metabolomic approach to agricultural sustainability
The multitasking microbe that turns CO₂ into minerals (Phys.org 8Jul2025)
└Cappa et al. (2025) Bacillus megaterium favours CO₂ mineralization into CaCO₃ over the ureolytic pathway
PFAS-eating bacteria discovered in Veneto soil (Phys.org 16Jun2025)
Bacteria hitch a ride on yeast puddles to zoom around (Phys.org 4Jun2025)
└Badal et al. (2025) Dynamic fluid layer around immotile yeast colonies mediates the spread of bacteria
Drought-fighting soil bacteria help wheat beat the heat (Phys.org 29May2025)
└Li et al. (2025) Drought-induced plant microbiome and metabolic enrichments improve drought resistance
Never-before-seen 'extreme' bacteria surrounded NASA robot before it was sent to Mars 18 years ago (LiveScience 21May2025)
What is a Healthy Microbiome? (NOVA 14Jan2014)
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