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

    • 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

  • 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

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