Bacteria: Size, Shape & Features

• The presentation covers bacteria, a topic in biomedical science, presented by Benjamin Tighe for the Eastman Dental Hospital Education Centre, part of LSBU.
• This study guide provides an overview of bacteria and intended leaning outcomes
• The aim is to classify bacteria by shape, size, environmental needs and examples associated with dentistry

Features of Bacteria

• Bacteria are small, single-celled microorganisms.
• Bacteria are an ancient life form and perform the same basic functions as other living cells.
• Bacteria lack chlorophyll.
• Bacteria usually has a single circular DNA chromosome found within the cytoplasm.
• Bacteria do not have membrane-bound organelles.

Size and Shape of Bacteria

• Bacteria size can be measured on a logarithmic scale, ranging from nanometers to millimeters, visualized using electron microscopes and light microscopes.
• Bacterial shapes include coccus (spherical), coccobacillus (oval), vibrio (curved rod), bacillus (rod-shaped), spirillum (spiral), and spirochete (corkscrew).

Bacterial Arrangements

• Arrangements of cocci include coccus (single), diplococci (pairs), streptococci (chains), staphylococci (clusters), tetrads (groups of four), and sarcina (cuboidal packets).
• Bacilli arrangements include coccobacillus (single), streptobacilli (chains of rods), diplobacilli (pairs of rods), and palisades (parallel arrangement).
• Other bacterial arrangements include vibrio (comma-shaped), filamentous, enlarged rods (Fusobacterium), corkscrew form (Borrelia burgdorferi), helical form (Helicobacter pylori), budding bacteria, and bacteria with stalks.

Structure of Bacteria

• Key bacterial structures include: flagellum, ribosomes, cytoplasm, nucleoid, plasma membrane, cell wall, capsule, and pilus.

Gram Staining

• Gram staining is a technique to distinguish and classify bacterial species into two groups: Gram-positive and Gram-negative.
• The technique was developed by Danish bacteriologist Hans Christian Gram.
• Gram-positive bacteria have a thick peptidoglycan cell wall.
• Gram-negative bacteria have a thin peptidoglycan layer and a thick lipopolysaccharide layer.
• The Gram staining process involves crystal violet, iodine, alcohol, and safranin.

Environmental Requirements

• Environmental requirements include these factors that needs to be described for each bacteria in workbook:
  • Moisture
  • Oxygen
  • Carbon dioxide
  • Temperature
  • pH
  • Light
  • Osmotic effect
  • Mechanical stress

Naming Bacteria

• Taxonomy is the systematic classification of organisms into ordered groups.
• Bacterial names combine genus and species names.
• Species names do not begin with a capital letter.
• Names are usually in italics.
• Generic names can be abbreviated, such as S. salivarius.
• Classification of Organisms
  • Kingdom: Procaryote
  • Division: Firmicutes
  • Subdivision: Low DNA content
  • Family: Streptococcaceae
  • Genus: Streptococcus
  • Species: Streptococcus salivarius

Bacteria and Dentistry

• Various bacteria are associated with dentistry, causing conditions such as tuberculosis, microbially-influenced corrosion (MIC), and infections with staphylococcus aureus.