Bacteria and Cyanobacteria

• Bacteria are bigger than viruses and are prokaryotic cells.
• Bacteria belong to the Domain Bacteria and Kingdom Eubacteria.
• Bacteria have existed for billions of years, representing an early stage of evolutionary history.
• Bacteria are small, about 100 times smaller than plant/animal cells, ranging from 0.2 to 10 micrometers (µm).
• 1 million micrometers equals 1 meter.
• Bacteria exist as either unicellular (one cell) or colonial (living in a colony).
• Colonial bacteria are a group of cells living together for mutual benefit, with each cell performing its own functions.
• Bacteria can be heterotrophic (absorbing nutrients/eating) or autotrophic (making their own food).
• Bacteria need moist conditions to thrive.

Phyla of Bacteria

• The Kingdom Eubacteria contains many phyla.

Cyanobacteria

• Cyanobacteria used to be called "Blue-green algae."
• These are autotrophic, which means they're photosynthetic.
• Found in freshwater and marine environments.
• Responsible for increasing oxygen levels on Earth.
• They can fix nitrogen, converting nitrogen gas into organic molecules that plants can use for growth.
• Cyanobacteria are indicators of water pollution, forming "algae blooms" that block sunlight and deplete oxygen.

Gram Positive Bacteria

• These comprise a large group which often live in soil.
• Some species can infect other organisms and cause disease.
• Streptomyces are cultured by pharmaceutical companies to produce antibiotics like streptomycin.

Proteobacteria

• Proteobacteria represent a large and diverse group.
• Gram-negative bacteria are capable of nitrogen fixation.
• Includes bacteria, such as Rhizobium, which help in nutrifying and denitrifying.
• These maintain a healthy gut.

Structure

• Prokaryotic cells lack membrane-bound organelles but may have vacuoles
• The nucleoid is a region containing a single circular DNA molecule.
• Plasmids are small, circular DNA pieces with non-essential DNA.
• Ribosomes make and synthesize proteins.
• The cell wall, made of peptidoglycan, provides strength and support.
• Pili are hair-like structures that aid in reproduction and attachment to cells.
• Flagella are whip-like tails used for movement, rotating like a motor.
• Vacuoles are membrane bound organelles
• The cell membrane is a semi-permeable layer regulating the passage of substances in and out of the cell.
• The cytoplasm is a gel-like substance housing organelles and facilitating metabolic reactions.

Identifying Bacteria

• Bacteria come in various shapes including coccus (spheres), bacillus (rods), and spirillum/spirillicates (spirals).
• Bacteria can be arranged as solitary (single cells), diplo (pairs), strepto (chains), staphylo (clusters), or sarcina (clusters of 4 and 8).
• The Gram stain identifies cell wall types using crystal violet (purple) and safranin (red).
• Gram-positive bacteria appear purple due to a thick peptidoglycan layer.
• Gram-negative bacteria appear red with a second outer membrane layer and a small peptidoglycan layer.
• Both Gram + and - can cause disease, but all do not.

Bacterial Movement

• Many bacteria are propelled by flagella.
• Some glide along secreting slime.
• Some adhere to surfaces or drift.

Metabolic Diversity

• Heterotrophs take in organic molecules for energy.
• Chemoheterotrophs take in chemicals (food).
• Photoheterotrophs use sunlight but need organic compounds for carbon.
• Autotrophs use energy to convert carbon dioxide into organic molecules.
• Photoautotrophs use light energy.
• Chemoautotrophs use energy from reactions with ammonia, hydrogen sulfide, nitrates, sulfur, or iron.
• The bacterial Kingdom has much diversity.
• The average human body is home to trillions of bacteria.

This lesson discusses the characteristics of bacteria, including their size, structure, and classification. It covers the distinction between unicellular and colonial bacteria, their modes of nutrition, and the conditions they need to thrive. It also introduces Cyanobacteria.