Microbial Genetics, Biotechnology, and Symbiotic Interactions

Comprehensive practice flashcards detailing concepts in recombinant DNA technology, protein purification, microbial bioproducts, and host-microbe symbiotic relationships.

Restriction enzymes

Proteins produced by bacteria as a defense response against bacteriophage infections that recognize and cleave specific DNA sequences in fragments to create recombinant DNA molecules.

Origin of replication

A DNA sequence on a plasmid that enables it to replicate independently from the host bacterial chromosome and be stably maintained within the host cell.

Homologous recombination

A molecular process that enables foreign DNA fragments to be retained, integrated, or reciprocal-exchanged into the host genome across regions of sequence homology.

Single crossover

A recombination event in which an entire suicide vector plasmid integrates into the host chromosome at an area of homology.

Double crossover

A reciprocal exchange occurring between two homologous regions that deletes or replaces the target intervening gene segment.

Suicide vector

A specialized delivery plasmid carrying disrupted gene fragments and selectable markers that cannot independently replicate inside the recipient host cell.

SacB counter selection

A negative selection strategy utilizing sucrose sensitivity to eliminate cells that retain the plasmid backbone when a resolving second crossover event fails to occur.

Selectable marker

A gene on an expression plasmid, such as an ampicillin resistance gene, used to identify and isolate host cells that successfully take up recombinant genetic information.

Protein affinity purification

A procedure in which a genetically fused peptide tag located at the $5'$ or $3'$ end of a gene binds an affinity column matrix, allowing unwanted host cell proteins to be washed away prior to target protein elution.

Coomassie-stained SDS-PAGE gel

An electrophoresis assay used to analyze and confirm the molecular size and presence of a purified recombinant protein.

Recombinant insulin production

The industrial process of cloning and expressing the coding sequences for the A chain and B chain separately in E. coli, harvesting both peptide chains, and combining them into functional insulin.

Conditional knockout animal

A genetically modified animal model in which a specific target gene is deleted at a precise developmental time point or tissue rather than constitutively throughout life.

Humanized mouse models

Genetically engineered mice carrying human genes, cells, or tissues used to investigate disease mechanisms, drug discovery, and immunotherapy.

In vivo gene therapy

A therapeutic strategy where viral vectors encoding a functional version of a target gene are introduced directly into the patient to achieve integrated therapeutic gene expression.

Ex vivo gene therapy

A therapy where patient cells are harvested, genetically modified outside the body via viral vectors or CRISPR, selected for the correct genomic change, and returned to the patient.

Lignin

A biodegradable-resistant phenolic polymer in plant cell walls that surrounds polysaccharides and requires pretreatment to liberate fermentable sugars.

Feedstock

The primary raw agricultural or biological material (such as cellulose, hemicellulose, starch, or sugarcane juice) used as a substrate for industrial microbial fermentation.

Bacillus megaterium

A bacterium known to accumulate PHBs and PHAs, which can be harvested to manufacture biodegradable bioplastics that degrade over time unlike conventional industrial plastics.

Polyhydroxybutyrate (PHB)

A biodegradable polymer accumulated as an energy reserve by certain bacteria that can be processed into bioplastics that naturally break down over time.

Pathobiont

A symbiotic microorganism that behaves harmlessly under normal conditions but has the capacity to cause pathology or become pathogenic under specific host circumstances.

Holobiont

An ecological entity comprising a host organism together with all of its associated symbiotic microbes.

Hologenome

The collective genetic material and protein-encoding capacity contributed by both the eukaryotic host and all associated microbial symbionts.

Mycobiont

The fungal partner that provides structural layered architecture within a lichen symbiosis.

Photobiont

The photosynthetic component of a lichen, consisting of photosynthetic green algae or cyanobacteria that synthesize organic nutrients.

Bacteroids

A differentiated, morphologically distinct form of endophytic bacteria residing inside plant root nodules that fix nitrogen under low oxygen concentrations.

Nitrogenase

An oxygen-sensitive microbial enzyme complex requiring $24\,\text{ATP}$ to reduce atmospheric nitrogen ($N_2$) into ammonia ($\text{NH}_3$).

Flavonoids

Plant root exudate compounds that provide nutrients and stimulate rhizobial bacteria to produce Nod factor signaling molecules.

Nod factor

Bacterial lipochitooligosaccharide signaling molecules synthesized in response to root flavonoids that induce root hair curling.

Infection thread

An internal tubular structure formed through the root hair cell wall and plasma membrane through which dividing rhizobia migrate into the plant root cortex.

Bacteriocytes

Specialized host insect cells designed to house and nurture primary endosymbionts.

Primary endosymbiont

An obligate, intracellular bacterial symbiont possessing a reduced genome that cannot survive outside its host and is maternally transmitted via eggs to developing embryos.

Secondary endosymbiont

A facultative microbial symbiont that retains a non-reduced genome, resides intercellularly or outside host cells, and can exist free-living in the external environment.

Coral microbiome challenges

Complications in managing marine holobionts due to extreme symbiont diversity, potential colonization of bleached corals by pathogens, fluctuating ocean temperatures, and variable nutrient conditions.