Bacterial Morphology and Diversity

• Morphology characteristics can be used to study bacterial diversity.

Bacteria

• Bacteria are often viewed as causes of disease in humans and animals.
• Some bacteria aid in digestion.
• Bacteria make up the base of food webs in many environments.
• Bacteria have extreme flexibility, with capacity for rapid growth, reproduction and great age.
• Bacteria can be photosynthetic or chemosynthetic but are mostly heterotrophic.
• Leptospira bacteria causes serious disease in livestock.

Bacterial Structure

• Biochemical processes in eukaryotes occur in the inner membrane of prokaryotes.
• Bacterial DNA is circular and resides in the cytoplasm within the nucleoid.
• Plasmids: Small loops of DNA are scattered within the bacterial inner membrane.
• Some bacteria have flagella (different microtubule structure than eukaryotes).
• Ribosomes are the structures in cells in which proteins are assembled.
• Bacterial ribosomes have different sized ribosomal subunits than those of eukaryotes.

Bacterial Shapes

• Bacteria have one of three cellular shapes: rods (bacilli), spheres or coccoid-shaped, and spirilla.
• Examples of Spheres (cocci) with scientific names:
  • Diplococci (Streptococcus pneumoniae)
  • Tetrad
  • Streptococci (Streptococcus pyogenes)
  • Staphylococci (Staphylococcus aureus)
  • Sarcina (Sarcina ventriculi)
• Examples of Rods (bacilli) with scientific names:
  • Chain of bacilli (Bacillus anthracis)
  • Flagellate rods (Salmonella typhi)
  • Spore-former (Clostridium botulinum)
• Examples of Spirals with scientifc names:
  • Vibrios (Vibrio Cholerae)
  • Spirilla (Helicobacter pylori)
  • Spirochaetes (Treponema pallidum)

Colony Morphology

• Each colony represents a single microbe that has replicated into a large group of identical clones.
• Colony shape helps determine identity.
• Whole colony descriptors include: punctiform, circular, rhizoid, irregular, filamentous.
• Edge descriptors include: entire, undulate, lobate, filamentous, curled.
• Surface descriptors include: smooth, glistening, rough, wrinkled, dry and powdery.
• Elevation descriptors include: flat, raised, convex, pulvinate, umbonate.

Reproduction

• Prokaryotic cell division occurs through binary fission, through the following steps:
  • Single DNA molecule is replicated.
  • Each copy attaches to a different part of the cell membrane.
  • Cells begin to pull apart.
  • Following cytokinesis, two cells of identical genetic composition result.

Experiment

• The purpose is to identify varieties of bacterial colonies, investigate bacterial species diversity by isolating, culturing and analyzing colonies or species.
• Varieties could be found in air, pond water, raw chicken, washed/unwashed hands, key boards and soil samples.
• Because bacteria can thrive almost anywhere, the hypothesis is that all environments tested will grow bacterial species.
• For chicken, soil, pond water, and keyboard samples, streak the plate with a streak plate method to isolate bacterial colonies.
• Leave agar plate open for air sample.
• Gently press unwashed, then washed hands on the agar.
• Label the petri dish with location, name and period.
• Wrap in Parafilm, and incubate the cultures for 48 hours at 22°C.
• Observe and interpret data
• Examine the morphology for each type of colony then describe it in detail.
• Organize your data.

Example Results

• In soil results SIZE, SHAPE, MARGIN, SURFACE and COLOR are recored
• Examples include:
  • 4mm Irregular Lobate Wavy Yellow/White
  • 3mm Irregular Lobate Wrinkled Brown/Yellow
  • 5mm Filamentous Filamentous Wrinkled Green/White

Explore bacterial diversity through morphology. Bacteria, often disease-causing, play crucial roles in digestion and food webs. Their flexible structure includes circular DNA in the nucleoid, plasmids, flagella, and unique ribosomes.