Bio2exam

What are the three domains of life?

Bacteria, Archaea, Eukarya

Describe the Bacteria domain

Prokaryotic organisms lacking a membrane-bound nucleus

Describe the Archaea domain

Prokaryotic organisms distinct from bacteria

Describe the Eukarya domain

Domain including organisms with membrane-bound nuclei

What is the difference between prokaryotic and eukaryotic ribosomes?

Prokaryotic Ribosomes: 70S (composed of smaller 30S and 50S subunits).

Eukaryotic Ribosomes: 80S (composed of larger 40S and 60S subunits).

How do the plasma membranes of Bacteria and Archaea differ?

Bacterial Membranes: Contain peptidoglycan.

Archaeal Membranes: Lack peptidoglycan, composed of proteins, glycoproteins, or polysaccharides.

What is Peptidoglycan?

Molecule found in bacterial cell walls

How do cell walls of Bacteria and Archaea differ?

Bacteria: Have peptidoglycan in their cell walls (Gram-positive: thick layer; Gram-negative: thin layer with an outer membrane).

Archaea: Lack peptidoglycan, may have pseudo-peptidoglycan or other complex molecules.

What is the difference in DNA polymerases between Bacteria and Archaea?

It is an enzymes involved in DNA replication!

Bacteria: Have 1 DNA polymerase.

Archaea: Have 3 DNA polymerases.

What is a Microbiologists?

Scientists studying microscopic organisms

What is binary fission?

A form of asexual reproduction in microorganisms where one cell divides into two identical cells.

What does coenocytic mean?

Microorganisms with nuclear divisions not followed by cell divisions

What are the four phases of bacterial growth? (In order)

Lag phase, Log phase, stationary phase, death phase

What happens during the lag phase of bacterial growth?

Initial phase with no immediate cell number increase

What happens during the log (exponential) phase of bacterial growth?

Phase of maximum growth rate and uniform properties

What happens during the stationary phase of bacterial growth?

Phase with constant viable cell numbers. Growth rate slows; death equals reproduction.

What happens during the death phase of bacterial growth?

Cells die at an exponential rate due to exhaustion of resources.

What is an Endospore?

Dormant, resistant structures formed by bacteria under stress, capable of withstanding extreme conditions.

What does Virulence mean?

Pathogenic bacteria's ability to cause disease

Antibiotics do what to bacterial growth?

Molecules killing or inhibiting bacterial growth

What is a biofilm?

A structured microbial community that adheres to surfaces and creates microenvironments, often resistant to antibiotics.

What are photoautotrophs?

Organism that uses light as an energy source to synthesize organic compounds

What is a facultative anaerobe?

Organism that can switch between aerobic and anaerobic metabolism

What is a sulfate reducer?

Organism that uses sulfate as a terminal electron acceptor in anaerobic respiration

What is bioremediation?

The use of microbes to clean up polluted sites by degrading toxins.

What are enrichment cultures?

Microbial cultures grown in controlled conditions to encourage the growth of specific microbes for further study.

What is metagenomics?

The study of genetic material recovered directly from environmental samples to identify species and pathways.

What is the microbiome?

The community of microbes that naturally inhabit the human body.

What is ectosymbiosis?

A symbiotic relationship where one organism remains outside the other.

What is endosymbiosis?

A symbiotic relationship where one organism resides inside the other.

Describe cocci bacterial shape

Roughly spherical bacterial cells occurring individually or in groups/chains

Describe bacillus bacterial shape

Rod-shaped bacterial cells that may form short chains

Describe spirilla bacterial shape

Rigid spiral-shaped bacterial cells

What is mycelium in bacteria?

Network of long, multinucleate filaments in bacteria

What are spirochetes?

Flexible helical-shaped bacteria

What is the bacterial plasma membrane?

A lipid-protein structure that serves as a barrier and a site for metabolic processes.

What are inclusion bodies?

Granules storing organic or inorganic materials in bacterial cells

What is 16S rDNA used for?

A universal molecule in bacteria used for studying phylogenetic relationships.

What is the nucleoid in bacteria?

An irregularly shaped region in prokaryotic cells containing the bacterial chromosome, without a membrane.

What is the structure of the prokaryotic chromosome?

A closed, circular DNA molecule with dozens to hundreds of genes, lacking histones.

Histones

DNA packaging proteins absent in prokaryotic chromosomes

What are plasmids?

Small, closed circular DNA molecules that exist and replicate independently of the bacterial chromosome.

What are the functions of plasmids in bacteria?

Small, circular DNA molecules that replicate independently of the chromosome and can carry genes that confer advantages like antibiotic resistance.

What are the methods of gene transfer in bacteria?

Includes transformation, transduction, and conjugation

Describe is gene transfer through transformation

DNA uptake from the environment

Describe is gene transfer through transduction

virus-mediated DNA transfer

Describe is gene transfer through conjugation

direct cell-to-cell contact

What is the function of the bacterial cell wall?

Provides shape, protects from osmotic lysis, and can contribute to pathogenicity.

What is the Gram stain, and how does it differentiate bacteria?

A dye system that distinguishes bacteria based on cell wall structure. Gram-positive bacteria appear purple, while Gram-negative bacteria appear pink.

How do Gram-positive and Gram-negative bacteria differ?

Gram-positive: Have thick peptidoglycan layers and stain purple.

Gram-negative: Have a thin peptidoglycan layer and an outer membrane, staining pink.

What are archaeal cell walls composed of?

Composed of proteins, glycoproteins, or polysaccharides, but lacking peptidoglycan.

What is a bacterial capsule?

An organized layer outside the bacterial cell wall that is not easily removed and can protect bacteria from the immune system.

What are methanogens?

Prokaryotes that produce methane as a byproduct of cellular respiration, often in anaerobic environments.

What was the Oxygen Revolution?

Cyanobacteria introduced oxygenic photosynthesis to Earth

What is nitrogen fixation, and why is it important?

The conversion of nitrogen gas (N₂) to ammonia (NH₃), which is essential for synthesizing proteins and nucleic acids.

How does nitrate pollution occur?

Caused by excess ammonia-based fertilizers, which lead to nutrient overloading in aquatic environments, creating anaerobic "dead zones."

What are Actinobacteria known for?

Filamentous bacteria abundant in soil, important for decomposition and producing antimicrobial compounds.

Chlamydiae

Obligate intracellular parasites found in mammals and birds

What are cyanobacteria, and what is their significance?

Photosynthetic prokaryotes that produce oxygen, playing a critical role in Earth's atmosphere and ecology.

What are vegetative cells in cyanobacteria?

Flattened or coccoid cells responsible for photosynthesis

What are heterocytes, and what do they do?

Specialized anaerobic cells in cyanobacteria responsible for nitrogen fixation.

What are akinetes in cyanobacteria?

Resting cells formed by cyanobacteria that help them survive under adverse conditions.

Baeocytes

Endospores formed by internal division of vegetative cells in cyanobacteria

Exospores

Spores cut off from one end of the parental cell

Ecology of cyanobacteria

Tolerant of environmental extremes. Thermophilic species can grow at temperatures up to 75°C. Often are primary colonizers. Can cause blooms in nutrient-rich ponds and lakes. Some produce toxins. Often form symbiotic relationships.

What are Firmicutes, and where are they found?

Extremely common in animal intestines. Live in symbiotic mutualism, aiding the digestive process. Several species used in agriculture and food processing. Others cause a variety of human diseases.

What are Proteobacteria, and where are they found?

Diverse in morphology. Some species form stalked cells while others form aggregates of cells organized as spore-forming fruiting bodies. Several species cause disease. Others play key roles in nitrogen cycling.

What is Escherichia coli (E. coli), and what is its significance?

Inhabitant of intestinal tracts of many animals. Used as indicator organisms for testing water for fecal contamination. Some strains are pathogenic causing gastroenteritis and urinary tract infections.

What diseases are caused by pathogenic enteric bacteria?

Salmonella: Causes typhoid fever and gastroenteritis.

Shigella: Causes bacillary dysentery.

Klebsiella: Causes pneumonia.

Bacteria—Spirochaetes (Spirochetes)

Distinguished by corkscrew shape and flagella. Parasitic, disease-causing species are propelled by motion into the tissues of their host. Other species are common in freshwater and marine habitats.

What are Crenarchaeota?

Also called eocytes. Found in harsh environments. May be autotrophic using CO or CO2 as carbon source.

What are Euryarchaeota, and where do they live?

A broad group of archaea that live in diverse environments, including high salt, acidic conditions, and methane-producing habitats.

What are Thaumarchaeota?

A recently recognized ancient lineage of archaea, abundant in oceans, estuaries, and terrestrial soils, thriving in moderate temperatures.

How does the lipid composition of bacterial membranes vary?

Lipid composition varies with environmental conditions. Bacteria usually lack sterols but may contain sterol-like molecules called hopanoids.

What are the main functions of the bacterial plasma membrane?

1. Retains cell shape.

2.Acts as a selectively permeable barrier.

3.Site for metabolic processes like respiration and photosynthesis.

4.Houses receptors to sense environmental conditions.

End of Prokaryotes PowerPoint

End of Prokaryotes PowerPoint

What is the basic definition of a virus?

A virus is an obligate intracellular parasite that requires a host cell for replication and reproduces at the expense of the host cell.

Are viruses considered living organisms?

Viruses are considered non-living because they cannot carry out metabolic processes or reproduce outside a host cell.

What are the basic characteristics of viruses?

Viruses are non-living particles called virions, consisting of a nucleic acid core (RNA or DNA) surrounded by a protein capsule (capsid). They can be enveloped or non-enveloped and vary greatly in size and shape.

What is the capsid in a virus?

The capsid is a protein shell that surrounds and protects the viral nucleic acid core. It can be enveloped (with a lipid membrane) or non-enveloped.

How are viruses classified based on their genome?

Viruses are classified by their genetic material: RNA or DNA, single-stranded (SS) or double-stranded (DS), and whether the genome is positive-sense, negative-sense, or ambisense.