Microbiology Lecture: Unusual Bacteria, Growth Curves & Intro to Viruses

Vocabulary flashcards covering unusual bacteria, bacterial growth phases, archaea, and introductory virus concepts from the lecture.

Binary Fission

Asexual reproductive process in which a bacterial cell elongates, replicates its genome, and divides into two genetically identical daughter cells.

Generation Time

The time required for a bacterial population to double during binary fission.

Lag Phase

Initial period of a bacterial growth curve when cell numbers remain constant as microbes adjust to a new environment.

Exponential (Log) Phase

Stage of rapid, doubling bacterial population growth where reproduction exceeds death.

Maximum Stationary Phase

Plateau stage of a growth curve where reproduction equals death and the population reaches carrying capacity.

Death Phase

Decline stage in a bacterial growth curve where cell death outpaces reproduction, causing population decrease.

Population Crash

Outcome of the death phase when all cells in a bacterial culture die, reducing the population to zero.

Minimum Stationary Phase

Low-level persistence of hardy bacteria (often as spores or in protected sites) after most of the population has died.

Carrying Capacity

Maximum number of organisms that an environment can support without being depleted or poisoned.

Obligate Intracellular Parasite

Microbe (e.g., viruses, Rickettsia, Chlamydia) that can reproduce only inside a living host cell.

Mycoplasma

Bacteria lacking a cell wall; cause walking pneumonia and must remain in warm, moist environments.

Rickettsia

Genus of gram-negative, obligate intracellular bacteria that cause diseases such as Rocky Mountain spotted fever.

Chlamydia

Genus of obligate intracellular bacteria; includes C. trachomatis, a common sexually transmitted pathogen.

Spirochete

Flexible, corkscrew-shaped bacteria possessing an axial filament for motility (e.g., Treponema, Borrelia).

Axial Filament (Endoflagellum)

Bundle of internal flagella wrapped around a spirochete, causing the whole cell to rotate and ‘drill’ through tissues.

Borrelia burgdorferi

Spirochete species that causes Lyme disease, transmitted by ticks; early sign may be a bull’s-eye rash.

Treponema pallidum

Spirochete species that causes syphilis, characterized by primary chancres, secondary rash, and tertiary gummas.

Chancre

Painless, ulcerative lesion at the portal of entry during primary syphilis.

Gumma

Large, destructive lesion of skin or organs characteristic of tertiary syphilis.

Bull’s-Eye Rash (Erythema migrans)

Expanding, ring-shaped rash often appearing in early Lyme disease.

Archaea

Prokaryotic, non-bacterial microorganisms lacking peptidoglycan cell walls; often extremophiles.

Methanogen

Archaeon that produces methane gas during metabolism; important in anaerobic environments.

Halophile

Microorganism (often archaeon) that thrives in high-salt environments such as the Great Salt Lake.

Thermophile

Organism that grows optimally at very high temperatures, e.g., in hot springs.

Acidophile

Microbe that prefers extremely acidic environments; some archaea are used to remediate acid mine drainage.

Bioremediation

Use of microorganisms to detoxify or clean up polluted environments (e.g., oil spills, heavy metals).

Endospore

Dormant, highly resistant bacterial structure enabling survival during harsh conditions and contributing to minimum stationary phase.

Virion

Complete, infectious viral particle existing outside a host cell; metabolically inert.

Naked (Non-enveloped) Virus

Virus consisting only of a nucleic acid core surrounded by a rigid protein capsid; lacks outer membrane.

Enveloped Virus

Virus whose capsid is wrapped in a lipid membrane stolen from the host cell, often bearing spike proteins.

Spike Protein

Surface projection on an enveloped virus that binds specific receptors on host cells, enabling entry.

HHV-3 (Varicella-Zoster Virus)

Human herpesvirus causing chickenpox on first exposure and shingles upon reactivation from nerve cells.

Primary Infection

Initial disease episode following first exposure to a pathogen (e.g., chickenpox from HHV-3).

Reactivation

Return of a latent virus to active replication, often triggered by stress or immune changes (e.g., shingles).

Carrying Capacity (Microbial)

Point at which environmental nutrients limit further population growth, leading to stationary phase.

T4 Bacteriophage

Well-studied virus that infects Escherichia coli; example of a bacteriophage.

Bacteriophage

Virus that specifically infects and often destroys bacteria.

Obligate Parasite

Organism or particle that must live in or on another living host to reproduce.

Typhoid Mary

Historical example of a human carrier who harbored Salmonella typhi in her gallbladder, constantly shedding bacteria.

Strep Tonsillar Carrier

Individual whose Streptococcus pyogenes hides in tonsillar crypts, leading to recurrent strep throat.

Biological Vector

Organism (e.g., tick) that transmits a pathogen while the pathogen completes part of its life cycle within the vector.