Overview of Bacteria

Shape:
- Cocci: Spherical
- Bacilli: Rod-shaped
- Spirilla: Spiral-shaped
Gram Staining:
- Gram-positive: Thick peptidoglycan layer; stain purple.
- Gram-negative: Thin peptidoglycan layer; stain pink.

Asexual: Primarily through binary fission, where one cell divides into two.
Horizontal Gene Transfer: Includes transformation, transduction, and conjugation, allowing genetic material exchange.

Ecological Role: Decomposers, nitrogen fixers, and primary producers in ecosystems.
Human Health: Beneficial bacteria in gut flora; some pathogenic bacteria cause diseases.
Industrial Use: Involved in fermentation (e.g., yogurt, antibiotics).

Examples include:
- Escherichia coli (E. coli): Can cause food poisoning.
- Streptococcus pneumoniae: Causes pneumonia.
- Mycobacterium tuberculosis: Causes tuberculosis.

Occurs when bacteria evolve to resist the effects of medications designed to kill them.
Contributes to public health challenges due to misuse of antibiotics.

Extremely diverse; found in various environments (extreme heat, cold, acidic, alkaline).
Estimated to be over 1 trillion species, with many still unidentified.

Single-celled microorganisms classified under the domain Bacteria.
They fall within the category of prokaryotic cells, characterized by the absence of a nucleus and organelles.

Cell Wall: Provides rigidity, shape, and protection from environmental stressors.
Cell Membrane: A semi-permeable barrier regulating the movement of substances in and out of the cell.
Cytoplasm: Gel-like substance where various cellular activities and biochemical reactions take place.
DNA: Typically organized as a circular chromosome residing in the nucleoid region, lacking a surrounding membrane.
Ribosomes: Organelles responsible for protein synthesis, significantly smaller than ribosomes found in eukaryotic cells.

Shape:
- Cocci: Spherical bacteria.
- Bacilli: Rod-shaped bacteria.
- Spirilla: Spiral-shaped bacteria.
Gram Staining:
- Gram-positive bacteria possess a thick peptidoglycan cell wall and stain purple.
- Gram-negative bacteria have a thinner peptidoglycan layer, resulting in a pink stain.

Autotrophic Bacteria: Capable of synthesizing their own food, such as photosynthetic bacteria.
Heterotrophic Bacteria: Depend on organic substances from their environment for nutrition, like decomposers.
Obligate Aerobes: Require oxygen for survival and growth.
Obligate Anaerobes: Cannot live in the presence of oxygen.
Facultative Anaerobes: Able to grow in the presence or absence of oxygen, demonstrating metabolic flexibility.

Asexual Reproduction: Primarily occurs through binary fission, a process where one bacterium divides into two identical cells.
Horizontal Gene Transfer: Mechanisms such as transformation, transduction, and conjugation facilitate the exchange of genetic material between bacteria.

Ecological Role: Essential as decomposers, nitrogen fixers, and primary producers, contributing to nutrient cycling in ecosystems.
Human Health: Beneficial bacteria inhabit the gut microbiome, aiding digestion; however, some bacteria are pathogenic and cause diseases.
Industrial Use: Employed in fermentation processes, contributing to the production of yogurt, cheese, and antibiotics.

Escherichia coli (E. coli): Associated with foodborne illnesses and can cause severe gastrointestinal problems.
Streptococcus pneumoniae: Responsible for pneumonia and other respiratory infections.
Mycobacterium tuberculosis: Causative agent of tuberculosis, a serious respiratory disease.

Developed when bacteria evolve mechanisms to withstand antibiotic treatments.
Considered a major public health challenge due to the overuse and misuse of antibiotics.

Bacteria exhibit immense diversity, thriving in extreme environments, including hot springs, deep seas, and highly acidic or alkaline conditions.
Estimates suggest over 1 trillion bacterial species exist, with a significant number yet to be formally identified.