Microbiology: Bacteria and Archaea

• Microbes, also known as microorganisms, are microscopic organisms that exist as single cells or cell clusters
• Microbes are ubiquitous in nature and are beneficial to life, but some can cause harm
• The study of microbes is called microbiology
• Microbes are highly diverse and are classified into various types based on their characteristics

Bacteria

• Bacteria are single-celled prokaryotic microorganisms
• They lack a nucleus and other membrane-bound organelles
• Bacteria have a cell wall composed of peptidoglycan
• They reproduce through binary fission, a type of asexual reproduction
• Bacteria are found in various environments, including soil, water, and the human body
• Some bacteria are beneficial and play important roles in nutrient cycling and digestion
• Pathogenic bacteria can cause various diseases in plants and animals, including humans
• Examples of bacterial diseases include pneumonia, tuberculosis, and food poisoning

Archaea

• Archaea are single-celled prokaryotic microorganisms, like bacteria
• They were initially classified as bacteria but are now recognized as a separate domain of life
• Archaea have unique cell walls and membranes that differ from bacteria
• Many archaea are found in extreme environments, such as hot springs, salt lakes, and acidic conditions
• These are referred to as extremophiles
• Archaea play important roles in nutrient cycling and can be used in various industrial processes
• Methanogens are archaea that produce methane as a metabolic byproduct
• Archaea are not known to cause diseases in humans

Fungi

• Fungi are eukaryotic microorganisms
• This means that they possess a nucleus and other membrane-bound organelles
• Fungi can be unicellular (yeasts) or multicellular (molds)
• They have cell walls composed of chitin
• Fungi reproduce through spores, which can be sexual or asexual
• Fungi are found in various environments, including soil, water, and air
• They play important roles in decomposition and nutrient cycling
• Some fungi are edible and are used in food production, for example, mushrooms, yeast in bread
• Pathogenic fungi can cause various diseases in plants and animals, including humans, for example, athlete's foot, ringworm

Protozoa

• Protozoa are unicellular eukaryotic microorganisms
• They lack a cell wall
• Protozoa are motile and can move using flagella, cilia, or pseudopodia
• They reproduce through binary fission, budding, or sexual reproduction
• Protozoa are found in various environments, including soil, water, and the human body
• Some protozoa are free-living, while others are parasitic
• Pathogenic protozoa can cause various diseases in humans, for example, malaria, Giardiasis

Algae

• Algae are photosynthetic eukaryotic microorganisms
• They can be unicellular or multicellular and contain chloroplasts with chlorophyll
• Algae produce oxygen through photosynthesis
• They are found in various aquatic environments, including oceans, lakes, and rivers
• Algae play important roles in aquatic food webs and are used in various industrial applications
• Some algae produce toxins that can be harmful to humans and animals
• Algae are not typically considered pathogenic

Viruses

• Viruses are non-cellular entities, they are not considered living organisms
• They consist of genetic material (DNA or RNA) enclosed in a protein coat called a capsid
• Viruses are much smaller than bacteria
• Viruses are obligate intracellular parasites
• They require a host cell to replicate
• Viruses infect various organisms, including bacteria, plants, and animals
• Viral infections can cause a wide range of diseases, for example, influenza, HIV

Prions

• Prions are infectious proteins that can cause neurodegenerative diseases
• They are misfolded versions of normal proteins found in the brain
• Prions can induce other proteins to misfold, leading to the formation of aggregates
• Prion diseases are rare but can be fatal, for example, mad cow disease, Creutzfeldt-Jakob disease
• Prions are highly resistant to inactivation and can persist in the environment for long periods