Microbiology: Microbial Growth, Genetics, Viruses, and Epidemiology

Comprehensive vocabulary flashcards covering microbial growth, microbial genetics, viruses, and epidemiology from Chapters 6, 8, 13, and 14.

Psychrophiles

Cold-loving microorganisms that grow over a range of $-10^\circ\text{C}$ to $20^\circ\text{C}$ with an optimal growth temperature of approximately $10^\circ\text{C}$.

Psychrotrophs

Microorganisms capable of growing between $0^\circ\text{C}$ and $20^\circ\text{C}\text{ to }30^\circ\text{C}$ (optimal around $25^\circ\text{C}$) that are primary causes of refrigerated food spoilage.

Mesophiles

Moderate-temperature-loving microorganisms with a growth range of $10^\circ\text{C}$ to $50^\circ\text{C}$ and an optimum growth temperature around $35^\circ\text{C}$.

Thermophiles

Heat-loving microorganisms that have an optimum growth temperature around $64^\circ\text{C}$ and grow in a temperature range between $40^\circ\text{C}$ and $72^\circ\text{C}$.

Hyperthermophiles

Microorganisms that grow in extreme heat with an optimum growth temperature around $95^\circ\text{C}$ and a range spanning $65^\circ\text{C}$ to $110^\circ\text{C}$.

Plasmolysis

The shrinkage of a cell's plasma membrane away from its cell wall resulting from osmotic water loss in a hypertonic environment.

Obligate Halophiles

Organisms (also called extreme halophiles) that require high osmotic pressure and high salt concentrations to grow.

Facultative Halophiles

Organisms that do not require high salt concentrations but can tolerate high osmotic pressure.

Obligate Aerobes

Organisms that require oxygen to grow; they possess superoxide dismutase (SOD) and catalase to neutralize toxic forms of oxygen.

Facultative Anaerobes

Microorganisms that can grow in the presence or absence of oxygen via fermentation or anaerobic respiration, showing greater growth in the presence of oxygen.

Obligate Anaerobes

Microorganisms unable to use oxygen and harmed by it because they lack the enzymes necessary to neutralize toxic forms of oxygen.

Aerotolerant Anaerobes

Organisms that cannot use oxygen for growth but tolerate its presence because they possess the enzyme superoxide dismutase (SOD).

Microaerophiles

Aerobic organisms that require oxygen concentrations lower than those found in normal air and produce lethal amounts of toxic oxygen forms if exposed to atmospheric levels.

Biofilms

Microbial communities adhering to surfaces surrounded by slime pillars that facilitate nutrient sharing, waste removal, and protection, communicating via quorum sensing.

Quorum Sensing

A mechanism of cell-to-cell communication where bacteria secrete chemical inducers to coordinate density-dependent behaviors.

Reducing Media

Culture media containing chemicals that combine with and deplete dissolved oxygen, used for growing obligate anaerobes.

Capnophiles

Microbes that grow best at high concentrations of $CO_2$, commonly cultivated using $CO_2$ packets or candle jars.

Differential Media

Culture media that allow distinguishing colonies of desired microbes from others on the same plate, such as blood agar showing patterns of hemolysis.

Enrichment Culture

A liquid medium designed to increase very small numbers of a desired organism to detectable levels.

Petroff-Hausser Cell Counter

A specialized counting chamber slide with a known volume and grid used to perform direct microscopic counts of bacteria.

Lag Phase

The growth curve period of intense metabolic activity preparing for population growth, with no increase in cell number.

Log Phase

The exponential growth phase during which bacterial cells divide at a constant logarithmic rate.

Stationary Phase

The period of equilibrium in a bacterial growth curve where microbial deaths balance the production of new cells.

Death Phase

The final growth phase where the microbial population decreases at a logarithmic rate until dying out.

Central Dogma

The molecular framework describing the sequential flow of genetic information: DNA is transcribed into mRNA, which is translated into protein.

Vertical Gene Transfer

The transfer of genetic information from parent organisms to offspring across generations.

Horizontal Gene Transfer

The transfer of genes laterally between cells of the same generation.

Okazaki Fragments

Short, discontinuous DNA segments synthesized on the lagging strand during DNA replication, initiated by RNA primers.

snRNPs

Small nuclear ribonucleoproteins located in the eukaryotic nucleus that remove intron-derived RNA and splice exon-derived RNA into mature mRNA.

Operon

A coordinated genetic unit consisting of an operator site, a promoter site, and the structural genes they regulate.

Inducible Operon

An operon that is default 'off' with a repressor bound to the operator, turned 'on' when an environmental inducer binds the repressor.

Repressible Operon

An operon that is default 'on' and actively transcribed until an environmental corepressor binds the repressor, activating it to block transcription.

Missense Mutation

A base substitution (point mutation) that changes a codon to encode a different amino acid.

Nonsense Mutation

A base substitution that alters an amino acid codon into a premature stop (nonsense) codon.

Frameshift Mutation

A mutation involving the insertion or deletion of one or more nucleotide pairs, altering the translational reading frame.

Thymine Dimers

Covalent cross-links between adjacent thymine bases caused by ultraviolet (UV) radiation that distort DNA and inhibit normal replication.

Photolyases

Enzymes that use visible light energy to split thymine dimers and restore normal DNA pairing.

Nucleotide Excision Repair

A DNA repair pathway where an endonuclease cuts damaged DNA, an exonuclease removes the fragment, DNA polymerase synthesizes replacement DNA, and DNA ligase seals the nick.

Plasmids

Self-replicating circular extrachromosomal DNA pieces ($1\%\text{ to }5\%$ the size of a bacterial chromosome) that often encode virulence factors or drug resistance.

Transposons

Mobile genetic elements containing insertion sequences (IS) encoding transposase, capable of moving from one chromosomal region to another.

Bacterial Transformation

The uptake of naked, donor DNA from the environment and its incorporation into a recipient bacterium's genome.

Bacterial Conjugation

The transfer of plasmid or chromosomal DNA between bacterial cells requiring direct cell-to-cell contact via sex pili and a mating bridge.

Transduction

The transfer of bacterial DNA from a donor cell to a recipient cell mediated by a bacteriophage.

Virion

A complete, fully developed, infectious viral particle consisting of nucleic acid surrounded by a protein coat.

Capsid

The outer protein coat of a virus composed of protein subunits called capsomeres.

T-Even Bacteriophage

A complex virus composed of an icosahedral head containing DNA, a helical sheath tail, a baseplate, pins, and tail fibers.

Plaques

Clear zones formed on a lawn of bacterial growth on an agar surface resulting from the lysis of cells by bacteriophages, measured in plaque-forming units (PFU).

Cytopathic Effect (CPE)

The visible deteriorative and morphological changes in host cell cultures resulting from viral infection.

Lytic Cycle

A viral life cycle in bacteriophages comprising attachment, penetration, biosynthesis, maturation, and lysis that results in host cell death.

Lysogeny

A cycle where phage DNA integrates into the host chromosome as a prophage without causing lysis, replicating along with the bacterium.

Phage Conversion

A change in the host cell's phenotype caused by the expression of prophage genes integrated into its chromosome.

Specialized Transduction

A process where specific bacterial genes adjacent to an excising prophage (such as the gal gene) are packaged into phage capsids and transferred to new host cells.

Provirus

Viral DNA synthesized by reverse transcriptase that integrates stably into a host cell chromosome.

Latent Viral Infection

An infection where the virus remains asymptomatic and dormant within the host for long intervals before reactivating (e.g., cold sores, shingles).

Persistent Viral Infection

A progressive viral disease occurring gradually over an extended period with continuous virion release, typically fatal (e.g., HIV/AIDS, subacute sclerosing panencephalitis).

Viroids

Infectious short pieces of naked RNA lacking a protein capsid that cause disease in plants.

Prions

Proteinaceous infectious particles lacking nucleic acids that cause spongiform encephalopathies like mad cow disease and Creutzfeldt-Jakob disease.

Microbial Antagonism

Competitive exclusion whereby normal resident microbiota inhibit invading pathogenic microbes by competing for nutrients, altering pH, or releasing harmful substances.

Commensalism

A symbiotic relationship in which one organism benefits while the other is completely unaffected (e.g., Staphylococcus epidermidis on skin).

Mutualism

A symbiotic relationship in which both participating organisms derive benefit (e.g., Escherichia coli in the large intestine).

Parasitism

A symbiotic relationship where one organism benefits at the physical expense and detriment of the host.

Opportunistic Pathogens

Organisms that do not cause disease in their normal habitat in a healthy individual but cause infection if access to compromised body sites occurs.

Koch's Postulates

Four experimental criteria used to establish that a specific infectious disease is caused by a specific microorganism.

Symptoms

Subjective changes in body function felt only by the patient as a result of disease.

Signs

Objective changes in body status that can be directly observed and measured by a clinician (e.g., fever, lesions).

Incidence

The number of individuals who develop a disease during a specific time interval, representing new case development.

Prevalence

The total number of individuals with a disease at a specified time point, accounting for both new and existing cases.

Endemic Disease

A disease that is constantly present at a steady rate within a given population.

Epidemic Disease

A disease acquired by many people in a given geographic area within a short duration.

Pandemic Disease

An epidemic disease that has spread worldwide.

Septicemia

Blood poisoning involving the active proliferation and multiplication of bacteria within the bloodstream.

Incubation Period

The time interval between initial exposure to a pathogen and the first appearance of signs or symptoms.

Prodromal Period

A short period following incubation characterized by early, mild, non-specific symptoms.

Period of Convalescence

The final stage of disease progression during which the body returns to its pre-diseased state.

Zoonoses

Diseases that are naturally transmissible from animals to humans.

Fomite

An inanimate object that serves as a vehicle for the indirect contact transmission of infectious pathogens.

Droplet Transmission

Transmission of pathogens through mucus droplets traveling less than $1\,\text{meter}$ from coughing, sneezing, or talking.

Mechanical Transmission

The passive transmission of pathogens via the exterior body parts (such as feet) of an arthropod vector to human hosts or food.

Biological Transmission

Vector transmission where the pathogen reproduces inside the arthropod vector and is transmitted via bites or defecation.

Healthcare-Associated Infections (HAIs)

Nosocomial infections acquired by patients while receiving care in healthcare facilities, resulting from an environment of hospital microbes, compromised hosts, and chains of transmission.

Compromised Host

An individual whose immune resistance to infection has been impaired by disease, therapy, surgical wounds, or burns.

Morbidity Rate

The number of individuals affected by a specific notifiable disease relative to the total population during a given time period.

Mortality Rate

The number of deaths caused by a specific disease in proportion to the total population within a given time period.