Microbiology: Microbial Growth Control, Genetics, and Biotechnology

Comprehensive vocabulary flashcards covering the control of microbial growth, microbial genetics, and recombinant DNA technology.

Biotechnology

The industrial or commercial use of microorganisms, cells, or cell components to make a useful product, such as foods, antibiotics, vitamins, and enzymes.

Recombinant DNA (rDNA) Technology

Techniques involving the insertion, deletion, or modification of genes in an organism to produce desired proteins or novel traits.

Vector

A self-replicating DNA molecule, such as a plasmid or viral genome, used to carry a foreign gene of interest into a recipient cell.

Clone

A population of genetically identical cells or organisms arising from a single progenitor cell, each carrying the newly introduced recombinant gene.

Site-Directed Mutagenesis

A molecular biology technique used to make a targeted, specific change in a DNA sequence in order to alter the resulting protein's amino acid code.

Restriction Enzymes

DNA-cutting enzymes naturally found in bacteria that cut double-stranded DNA at specific recognition nucleotide sequences and cannot digest host bacterial DNA protected by methylated cytosines.

pUC19

A standard plasmid cloning vector containing an origin of replication ($\text{ori}$), an ampicillin-resistance marker gene ($amp^R$), and a multiple cloning site within the $\beta$-galactosidase gene ($lacZ$) containing cleavage sites for enzymes such as HindIII, BamHI, and EcoRI.

Polymerase Chain Reaction (PCR)

An in vitro enzymatic procedure used to rapidly make multiple copies of a targeted DNA region using repetitive thermal cycles of strand denaturation at 94^\rigtht^\text{C}, primer annealing at $60^\text{C}$, and DNA polymerase extension at $72^\text{C}$.

Electroporation

A physical method of introducing foreign DNA into cells by applying brief electrical pulses that generate transient microscopic pores in the plasma membrane.

Protoplast Fusion

A gene transfer technique where cell walls are enzymatically stripped to create protoplasts, which are subsequently merged using polyethylene glycol to allow genetic recombination.

Microinjection

The direct introduction of foreign microscopic DNA solutions into an animal cell or egg using an extremely fine glass micropipette under a microscope.

Genomic Library

A comprehensive collection of recombinant clones, maintained within plasmids or bacteriophages, that collectively contain fragments representing an organism's entire genome.

Complementary DNA (cDNA)

An artificial DNA molecule synthesized in vitro from a processed eukaryotic mRNA template using the viral enzyme reverse transcriptase, thereby omitting all non-coding introns.

Blue-White Screening

A selection method identifying recombinant bacteria; insertion of foreign DNA interrupts the plasmid $lacZ$ gene, preventing $\beta$-galactosidase synthesis and resulting in white colonies on media with X-gal, whereas non-recombinants turn blue.

Colony Hybridization

A technique using a labeled, single-stranded nucleic acid probe that base-pairs with a complementary target sequence on a membrane transfer to locate specific cloned genes in bacterial colonies.

Southern Blotting

A method in which restriction-cleaved DNA fragments separated by agarose gel electrophoresis are blotted onto a nitrocellulose filter and hybridized with a labeled DNA probe to identify specific sequences.

Ti Plasmid

A tumor-inducing plasmid of the plant bacterium Agrobacterium tumefaciens, engineered as a vector to transfer foreign genes (T-DNA) into the nuclear genome of plant host cells.

Sterilization

The complete destruction or removal of all viable forms of microbial life, including bacterial endospores, from an object or material.

Commercial Sterilization

A targeted heat treatment process sufficient to destroy the endospores of Clostridium botulinum in canned food products while avoiding severe food quality degradation.

Disinfection

The destruction or inactivation of vegetative pathogenic microorganisms on inanimate objects or non-living surfaces using physical or chemical agents.

Antisepsis

The chemical treatment and destruction of vegetative pathogens located directly on living biological tissue.

Degerming

The mechanical reduction or physical removal of microbes from a limited surface area, such as washing with soap or wiping skin around an injection site with an alcohol swab.

Sanitization

The reduction of microbial populations on eating utensils and food-preparation surfaces to levels deemed safe by public health standards.

Bacteriostasis

A condition or treatment that arrests and inhibits bacterial growth and reproduction without directly killing the microbial cells.

Microbial Death Curve

A graphic plot illustrating that microbial populations treated with heat or chemicals die at a constant logarithmic rate, where each logarithmic cycle reduction corresponds to killing $90\%$ of remaining viable cells.

Thermal Death Point (TDP)

The lowest temperature at which all microorganisms in a particular liquid culture suspension are killed within exactly $10\,\text{min}$.

Thermal Death Time (TDT)

The minimal length of time required to completely kill all microorganisms in a liquid culture at a specified, fixed temperature.

Decimal Reduction Time (DRT)

The time in minutes required to kill $90\%$ of a microbial population at a defined temperature, representing a single decimal or 1-log reduction.

Autoclave

A specialized pressure chamber that uses moist steam under pressure, typically operating at $121^\circ\text{C}$ at $15\,\text{psi}$ for $15\,\text{min}$, to achieve reliable sterilization.

Pasteurization

The application of mild, controlled heat, such as High-Temperature Short-Time treatment at $72^\circ\text{C}$ for $15\,\text{sec}$, to destroy heat-sensitive pathogens and spoilage microbes in beverages.

High-Efficiency Particulate Air (HEPA) Filter

A physical screen filter capable of removing airborne particles and microorganisms greater than $0.3\,\mu\text{m}$ in diameter.

Use-Dilution Test

A standard laboratory evaluation of chemical disinfectants where metal cylinders coated with dried test bacteria are submerged in disinfectant for $10\,\text{min}$ at $20^\circ\text{C}$ and transferred to nutrient broth to check for survival.

Disk-Diffusion Method

An agar-plate assay in which chemical agent-saturated paper filter disks are placed on a bacterial lawn to evaluate antimicrobial efficacy by measuring the resulting diameter of the clear zone of inhibition.

O-phenylphenol

A phenolic compound derived from phenol by chemical alteration, commonly used as an active disinfectant ingredient in commercial disinfectant sprays and surface cleansers to disrupt microbial plasma membranes.

Hexachlorophene

A bisphenol disinfectant composed of two phenolic rings connected by a methylene bridge, highly effective against Gram-positive staphylococci and streptococci.

Biguanides

A category of broad-spectrum antimicrobials, including chlorhexidine, that damage microbial cellular membranes and are frequently used as surgical hand scrubs and preoperative skin antiseptics.

Iodophor

An antimicrobial complex consisting of elemental iodine bound to an organic carrier molecule (such as povidone in Betadine), allowing slow release of iodine with reduced staining and skin irritation.

Quaternary Ammonium Compounds (Quats)

Cationic, surface-active detergents containing a central nitrogen atom with four organic groups, effective against Gram-positive bacteria, fungi, and enveloped viruses by denaturing proteins and disrupting membranes.

Oligodynamic Action

The antimicrobial property whereby minute, trace amounts of heavy metal ions, such as silver ($\text{Ag}$), mercury ($\text{Hg}$), and copper ($\text{Cu}$), denature microbial cellular proteins.

Ethylene Oxide

A highly penetrating, cyclic ether gaseous sterilant that replaces labile hydrogen atoms in microbial protein functional groups (alkylating agent), sterilizing heat-sensitive medical supplies at ambient temperatures.

Genetics

The branch of biological science that studies heredity, including what genes are, how they store information, how they express traits, and how they replicate and transfer across generations.

Genome

The complete genetic complement of an organism or virus, including its chromosomes and any non-chromosomal genetic elements like plasmids.

Gene

A defined nucleotide sequence of double-stranded DNA that encodes a functional cellular product, most commonly a polypeptide or a functional RNA.

Genotype

The specific genetic composition and collection of genes present within an organism's DNA.

Phenotype

The observable physical, structural, enzymatic, and physiological properties or manifestations of an organism resulting from gene expression.

Central Dogma

The fundamental concept of molecular biology stating that genetic information flows from DNA through transcription into RNA, which is subsequently translated into functional protein.

Semiconservative Replication

The mechanism of DNA replication in which each resulting double-stranded daughter DNA molecule is composed of one conserved parental template strand and one newly synthesized daughter strand.

DNA Helicase

An ATP-dependent replication enzyme that unwinds and separates parental double-stranded DNA into single strands ahead of the advancing replication fork.

DNA Polymerase

The primary enzyme responsible for synthesizing new DNA strands in the $5' \rightarrow 3'$ direction by adding matching deoxynucleotides, as well as removing RNA primers and proofreading for mismatched pairs.

DNA Ligase

An enzyme that forms covalent phosphodiester bonds to join adjacent DNA segments, such as sealing breaks between discontinuous Okazaki fragments on the lagging strand.

Okazaki Fragments

Short, discontinuously synthesized segments of DNA produced on the lagging template strand during replication, initiated by short RNA primers.

Transcription

The biochemical process in which RNA polymerase synthesizes a complementary single-stranded RNA molecule from a specific DNA template strand in the $5' \rightarrow 3'$ direction.

Promoter

A specific regulatory nucleotide sequence on DNA where RNA polymerase and transcription factors bind to initiate the transcription of a gene or operon.

Introns

Non-coding intervening sequences within eukaryotic precursor mRNA transcripts that are excised by spliceosomes prior to nuclear export and translation.

Exons

The protein-coding regions of a eukaryotic gene and mature mRNA transcript that remain joined together following RNA splicing to direct polypeptide synthesis.

Codon

A specific triplet sequence of three consecutive nucleotide bases in an mRNA molecule that designates a particular amino acid or signals translation termination.

Anticodon

A triplet sequence of three ribonucleotides situated in a loop of a transfer RNA (tRNA) molecule that base-pairs with a complementary mRNA codon during translation.

Operon

A coordinate genetic regulatory structure in bacteria consisting of a promoter, an operator, and one or more contiguous structural genes regulated together.

Inducible Operon

A bacterial operon (exemplified by the lac operon) that is normally inactive because a repressor is bound to the operator, but is turned on when a specific inducer molecule inactivates the repressor.

Repressible Operon

A bacterial operon (exemplified by the trp operon) that is continuously expressed until an abundant corepressor binds to an inactive repressor, enabling it to bind the operator and block transcription.

microRNAs (miRNAs)

Small, single-stranded non-coding RNA molecules transcribed from eukaryotic genomes that bind complementary target mRNA sequences to repress translation or accelerate mRNA degradation.

Point Mutation

A localized genetic alteration in which a single base pair in a DNA sequence is substituted, added, or deleted.

Missense Mutation

A point mutation wherein a single nucleotide base substitution alters an mRNA codon so that it encodes a different amino acid in the resulting polypeptide.

Nonsense Mutation

A base substitution mutation that converts an amino acid-specifying sense codon into a premature stop codon, terminating translation early and generating a truncated protein.

Frameshift Mutation

A mutation involving the insertion or deletion of one or more nucleotide pairs (not divisible by three), which alters the translational triplet reading frame downstream.

Mutagen

Any physical agent (such as UV light or X-rays) or chemical agent (such as nitrous acid or ethidium bromide) that directly increases the rate of DNA mutation above spontaneous levels.

Ames Test

A biological assay utilizing a histidine-auxotrophic mutant of Salmonella to screen prospective chemical agents for mutagenicity and potential carcinogenicity by quantifying the reversion rate back to histidine prototrophy.

Vertical Gene Transfer

The transmission of genetic material from parent organisms to their biological progeny during reproduction across successive generations.

Horizontal Gene Transfer

The lateral passage of genes between donor and recipient cells belonging to the same generation through transformation, conjugation, or transduction.

Transformation

A mechanism of horizontal gene transfer in which a competent bacterial recipient cell takes up free, naked foreign DNA fragments from its surrounding liquid environment.

Conjugation

The direct horizontal transfer of genetic material (such as an F plasmid) from a donor bacterial cell to an adjacent recipient cell via physical cell-to-cell contact through a sex pilus.

Transduction

A bacterial gene transfer process wherein host bacterial chromosomal DNA is accidentally packaged inside a bacteriophage capsid and transferred into a new recipient bacterium during viral infection.

Plasmid

A small, circular, double-stranded, self-replicating extrachromosomal DNA molecule present in bacteria that carries accessory genes not essential for basic survival under non-stress conditions.

R Factor

A specialized bacterial plasmid carrying genes that confer antibiotic resistance along with genes required for conjugative transfer to other bacterial cells.