Bacteria: Structure and Characteristics

Bacteria

• Small, single-celled microorganisms
• Ancient life form
• Similar basic functions as other living cells, but lack chlorophyll
• Mostly have a single circular DNA chromosome found within their cytoplasm
• Lack membrane-bound organelles

Size and Shape of Bacteria

• Vary in size
• Have different shapes: coccus (round), bacillus (rod-shaped), spirillum (spiral)
• Can be arranged in various formation, for example: chains (strepto-), clusters (staphylo-), pairs (diplo-)

Structure of Bacteria

• Flagellum: Tail-like structure for movement
• Ribosomes: Synthesize proteins
• Cytoplasm: Gelatinous substance within the cell membrane
• Nucleoid: Contains the bacterial DNA
• Plasma membrane: Encloses the cytoplasm and regulates what enters and exits
• Cell wall: Provides structural support and shape
• Capsule: Outer layer that protects the bacteria and helps it adhere to surfaces
• Pilus: Hair-like appendages that help bacteria attach to surfaces

Gram Staining

• A technique to differentiate bacteria into two groups: Gram-positive and Gram-negative
• Developed by Hans Christian Gram, a Danish bacteriologist
• Based on the differences in cell wall structure:
  • Gram-positive bacteria have a thick peptidoglycan layer in their cell wall
  • Gram-negative bacteria have a thin peptidoglycan layer and a thick outer membrane made of lipopolysaccharide

Environmental Requirements

• Carbon: For energy and growth
• Moisture: Essential for life
• Oxygen: Some bacteria require oxygen, some don't, and some are poisoned by it
• Carbon dioxide: A byproduct of respiration and necessary for some bacteria
• Temperature: Each bacterium has an optimal temperature range for growth
• pH: Each bacterium has an optimal pH range for growth
• Light: Some bacteria require light for photosynthesis
• Osmotic effect: Influences water movement across the cell membrane
• Mechanical stress: Can affect bacterial growth

Naming Bacteria

• Classification of organisms into ordered groups is called TAXONOMY
• The name is usually a combination of the last two ranks: Genus and Species
• Species does not begin with a capital letter
• Name is usually in italics
• Generic names can be abbreviated e.g. S.
• Example: Streptococcus mutans

Classification of Bacteria

• Kingdom: Procaryote
• Division: Firmicutes
• Subdivision: Low DNA content
• Family: Streptococcaceae
• Genus: Streptococcus
• Species: Streptococcus mutans

Explore the fascinating world of bacteria in this quiz, focusing on their basic functions, sizes, shapes, and structural components. Test your knowledge about their ancient origins, cellular structures, and how they vary in form and function.