Eubacteria True Bacteria: Characteristics and Examples

Eubacteria, also called true bacteria, are single-celled prokaryotic microorganisms found almost everywhere on Earth, from soil and water to the human intestine and hot springs. Unlike the cells of plants and animals, a bacterial cell has no membrane-bound nucleus; its genetic material floats freely in the cytoplasm. They are among the smallest and oldest living things known.

True bacteria matter because they run many of nature's essential services. They decompose dead matter and recycle nutrients, fix atmospheric nitrogen for plants, ferment milk into curd, and produce life-saving antibiotics. At the same time, a few species cause diseases like tuberculosis and cholera, so understanding them is important for health, farming and industry.

Key Concepts

• Prokaryotic cell: no true nucleus and no membrane-bound organelles; DNA is a single circular chromosome in a region called the nucleoid.
• Cell wall: made of peptidoglycan (also called mucopeptide), which gives the cell its shape and protection.
• 70S ribosomes: smaller than the 80S ribosomes of plant and animal cells; site of protein synthesis.
• Shapes: coccus (spherical), bacillus (rod-shaped), spirillum (spiral) and vibrio (comma-shaped).
• Nutrition: autotrophic bacteria make their own food by photosynthesis or chemosynthesis, while heterotrophic bacteria depend on organic matter.
• Extra structures: some bacteria have flagella for movement, pili for attachment, and a slimy capsule for extra protection.

How It Works

Bacteria mostly reproduce by binary fission, a simple asexual process. First the circular DNA copies itself, then the cell grows longer, and finally a wall forms across the middle, splitting one cell into two identical daughter cells. Under warm, moist, nutrient-rich conditions this can happen every 20 minutes, so one cell can become millions in a few hours.

Bacteria also exchange genes without reproduction. In transformation, a cell takes up free DNA from its surroundings; in transduction, a virus carries DNA from one bacterium to another; and in conjugation, two cells join through a tube called a pilus and pass a small DNA ring called a plasmid. These tricks spread useful traits, such as antibiotic resistance, very quickly.

Worked Example

Question: A culture of E. coli doubles every 20 minutes. If it starts with 50 cells, how many cells are there after 3 hours?

Step 1: Convert time to minutes: 3 hours = 180 minutes.

Step 2: Number of generations = 180 / 20 = 9.

Step 3: Use the growth formula N = N0 x 2^generations = 50 x 2^9.

Step 4: 2^9 = 512, so N = 50 x 512 = 25,600 cells.

Answer: 25,600 cells after 3 hours.

Real-World Applications

• Dairy industry: Lactobacillus bacteria ferment milk sugar into lactic acid to make curd, cheese and yoghurt.
• Medicines: Streptomyces bacteria produce antibiotics such as streptomycin.
• Farming: Rhizobium lives in the root nodules of legumes and fixes atmospheric nitrogen into a form plants can use.
• Waste treatment: bacteria break down sewage and organic waste in treatment plants and produce biogas.
• Disease control: knowing bacteria like Mycobacterium tuberculosis and Vibrio cholerae helps doctors diagnose and treat infections.

Eubacteria are simple prokaryotic cells with a peptidoglycan wall and circular DNA. They multiply fast by binary fission, swap genes through transformation, transduction and conjugation, and touch our lives daily through food, farming, medicine and disease.