Study Guide: Extremophiles, Viruses, and DNA Replication

Extremophiles

Organisms that thrive in extreme conditions.

Growth Rates

Vary significantly; e.g., hot spring bacteria vs. deep-sea sediment microbes.

Factors

Nutrition, temperature, pH, and specific physical parameters.

Normal Growth Conditions

Typically anthropocentric.

Psychrophiles

0°C - 20°C.

Mesophiles

15°C - 45°C.

Thermophiles

40°C - 80°C.

Hyperthermophiles

65°C - 121°C.

Cellular Adaptations

Protein and membrane structural changes.

Enzymes and Membranes

Adjust rigidity and flexibility to suit temperature ranges.

Astrobiology

Predicts extraterrestrial life.

Human Technology

Provides tools and insights.

Biodiversity

Enhances understanding of life's adaptability.

Heat-Shock Response

Activates stress response genes for survival.

Long-Term Survival

Protective mechanisms in organisms.

Living Without Oxygen

Many microorganisms are anaerobes.

Anaerobic Respiration

Uses non-oxygen terminal electron acceptors.

Oxygen-Sensitive

Some organisms are vulnerable to oxygen presence.

Organic Electron Acceptors

Used in fermentation, typically oxygen-neutral.

Anaerobes

Survive in low oxygen; include obligate, aerotolerant, and facultative anaerobes.

Reactive Oxygen Species (ROS)

Types: Singlet oxygen, superoxide, hydrogen peroxide, hydroxyl radicals.

Damage

Affects DNA, proteins, and lipids.

High Energy Yield

Used in aerobic respiration.

Mitochondrial Respiration

Involves electron transport chain.

Strict Anaerobes

Die in presence of oxygen.

Microaerophiles

Require low oxygen levels.

Sterilization

Kills all living cells, spores, and viruses.

Disinfection

Removes pathogens but may not sterilize.

Antisepsis

Removes pathogens from living tissues.

Sanitation

Reduces microbial population to safe levels.

Low Temperature

Slows growth; refrigeration for preservation.

High Temperature

Kills microbes; pasteurization and sterilization.

Moist heat

More effective than dry heat.

Pressure

Used in autoclaving for sterilization.

Filtration

Removes microbes from air and liquids.

UV Light

Low energy, surface sterilization.

Gamma Rays/X-Rays

High energy, penetrates materials.

Antimicrobial Agents

Example: Quats.

Properties

Amphipathic; have hydrophobic and hydrophilic ends.

Function

Disrupt cell membranes and structures.

Natural Predators

Potential use in human tissue.

Bacterial Viruses

Bacteriophages used in treating infections.

Predatory Bacteria

Target harmful bacteria, safe for humans.

Microbial Classification

Based on growth temperature.

Extremophiles' Role

Crucial for understanding life's limits and potential.

Heat-Shock Proteins

Essential for stress response and adaptation.

Anaerobic Growth

Highlights diversity in metabolic pathways.

Oxygen Dynamics

Understanding ROS and anaerobic environments.

Microbial Control

Methods for reducing or eliminating microbial presence.

Detergents and Biological Control

Use of chemical and natural methods for microbial management.

Virions

Noncellular particles that infect host cells to reproduce.

Genome

DNA or RNA within a protein capsid; can be double or single-stranded, linear or circular.

Structure

Capsid and genome; some have envelopes derived from host cell membranes.

Acute Viruses

Limit host population density.

Survivors

Undergo selection for resistance.

Diversity

Increases in the ecosystem, affecting overall ecological balance.

Intracellular Replication Complex

Converts host cells into virus factories.

Integration

Viral genome integrates into host DNA, replicating with the host.

Prophage

Integrated viral genome, can confer new traits to host.

Virion

Inert particle outside host.

Intracellular Replication

Active within host cells.

Marine Viruses

Control algal blooms, recycle nutrients.

Capsid Structures

Symmetrical: Icosahedral (e.g., herpesvirus) or filamentous (e.g., TMV).

Complex

Tailed viruses like T4 bacteriophage with head and tail structures.

Asymmetrical

Example: T4 bacteriophage with complex multipart structures.

Viroids

RNA molecules infecting plants, lack protein capsid.

Prions

Infectious proteins causing diseases like BSE, lack nucleic acid.

Envelopes

Derived from host membranes, contain spikes for attachment.

Spikes

Aid in host cell attachment and entry.

Host Receptors

Specific interactions for entry, e.g., ACE2 for SARS-CoV-2.

Endocytosis

Common entry method for enveloped viruses.

Uncoating

Releases genome into cytoplasm for replication.

Biosynthesis

Viral genome replication and protein synthesis.

Assembly

Virions assembled at host membrane.

Virions

Virions assembled at host membrane.

Release

Virions exit host cell, often by budding.

Oncogenic Viruses

Can cause cancer by altering host cell growth.

Integration

Viral genes integrate into host chromosomes, affecting cell cycle.

Virion Structure

Understanding capsid and genome variations.

Viral Replication

Intracellular processes and integration into host DNA.

Diversity

Structural variations among viruses, including viroids and prions.

Pathogenesis

How viruses cause disease and affect ecosystems.

Microbial Replication

Microbes replicate DNA quickly, some doubling populations in less than 15 minutes.

Replisome

Complex machine involving many proteins for DNA replication.

Semiconservative Replication

Each new DNA helix has one parental and one newly synthesized daughter strand.

Nucleotide Addition

New nucleotides added to the 3' end of the growing DNA strand.

DNA Polymerase

Requires a primer to add nucleotides.

DnaA-ATP

Binds to DNA, opening the helix at oriC.

DNA Unwinding

DnaB (helicase) unwinds the DNA, using ATP.

Primase

Synthesizes RNA primers on each template strand.

DNA Pol III

Adds nucleotides to the RNA primer, synthesizing new DNA.

Origin of Replication (oriC)

Specific DNA sequence where replication begins.

DnaA

Initiator protein that binds to oriC.

DnaB (Helicase)

Unwinds DNA strands.

DNA Ligase

Seals gaps in the lagging strand.

Sliding Clamp

Holds DNA polymerase in place.

Leading Strand

Continuous synthesis towards the replication fork.

Lagging Strand

Discontinuous synthesis away from the fork, forming Okazaki fragments.

Okazaki Fragments

Short DNA sequences synthesized on the lagging strand.

Termination Sites (ter)

Located opposite the origin, where replication ends.