Bacteria

Comprehensive vocabulary flashcards covering Grade 11 Life Sciences microbiology notes on bacteria: cellular structures, metabolic categories, reproduction, genetic mechanisms, TB pathology, antibiotic resistance, population growth phases, and environmental factors.

Bacteria

Microscopic, single-celled prokaryotic organisms whose DNA is not enclosed in a membrane-bound nucleus.

Pathogen

A microorganism or biological agent capable of causing disease.

Antonie van Leeuwenhoek

Scientist in the $1670\text{s}$ who used handmade microscopes to observe bacteria, which he referred to as "animalcules".

Louis Pasteur

Scientist in the $1800\text{s}$ who helped establish germ theory and demonstrated that microorganisms are involved in fermentation and spoilage.

Robert Koch

Scientist in the late $1800\text{s}$ who linked specific microorganisms to particular diseases and identified the bacterium responsible for TB.

Germ theory

The principle stating that many infectious diseases are caused by microorganisms entering and multiplying within a host.

Cocci

Spherical bacterial cells that occur singly, in pairs (diplo-), chains (strepto-), or clusters (staphylo-).

Bacilli

Rod-shaped bacterial cells that occur as single rods, pairs, or chains.

Vibrios

Curved or comma-shaped bacterial cells, usually occurring as separate curved rods.

Spirilla / Spirochaetes

Spiral- or corkscrew-shaped bacterial forms characterized by twisted cells.

Capsule

A slimy external layer found on some bacteria that provides protection against drying and host defences, and assists in attachment and biofilm formation.

Bacterial Cell Wall

A rigid layer containing peptidoglycan that maintains cell shape and prevents osmotic bursting.

Nucleoid

The region within a bacterial cell containing the main, usually circular DNA molecule that controls inherited characteristics.

Plasmid

A small, extra loop of DNA (often circular) that replicates independently, can carry antibiotic-resistance genes, and may be transferred between bacteria.

$70\text{S}$ Ribosomes

Bacterial organelles responsible for protein synthesis.

Pili / Fimbriae

Surface structures used for attachment; specialized sex pili participate in direct DNA transfer during conjugation.

Outer Membrane

An additional protective barrier in Gram-negative bacteria that can restrict the entry of some antibiotics.

Endospore

A tough, dormant survival structure formed by some bacteria in harsh conditions; it does not serve a reproductive function.

Binary Fission

The asexual division of one parent bacterial cell into two genetically similar daughter cells without the fusion of gametes.

Conjugation

A mechanism of genetic transfer where DNA (often a plasmid) passes directly between bacteria through physical contact.

Transformation

The process by which a bacterium takes up free, naked DNA from its surrounding environment.

Transduction

The transfer of DNA between bacterial cells mediated by a bacteriophage.

Photoautotrophs

Autotrophic bacteria that utilize light energy to convert inorganic carbon ($\text{CO}_2$) into organic substances.

Chemoautotrophs

Autotrophic bacteria that obtain energy from chemical reactions to synthesize organic substances from inorganic carbon ($\text{CO}_2$).

Saprotrophs

Heterotrophic bacteria that break down dead organic matter to obtain nutrients, facilitating decomposition and nutrient recycling.

Obligate Aerobes

Bacteria that require oxygen for aerobic respiration to survive and grow.

Obligate Anaerobes

Bacteria that grow exclusively in the absence of oxygen and to which oxygen is harmful.

Facultative Anaerobes

Bacteria that can grow with or without oxygen by switching their metabolic pathways.

Aerotolerant Anaerobes

Bacteria that do not use oxygen for metabolic processes but tolerate its presence.

Mycobacterium tuberculosis

The rod-shaped bacillus bacterium responsible for causing tuberculosis (TB).

Latent TB Infection

A condition in which TB bacteria remain dormant in the body; the individual shows no symptoms and cannot transmit the disease.

Active TB Disease

A stage of TB where bacteria multiply and cause symptoms (such as a persistent cough, fever, night sweats, and weight loss) and can be infectious when affecting the lungs or throat.

Tuberculin Skin Test (Mantoux/PPD)

A test where tuberculin is injected into the skin, measuring the resulting firm swelling (induration) after $48\text{--}72\text{ hours}$; it identifies infection but cannot differentiate latent from active disease.

BCG Vaccination

A vaccine administered to provide protection against severe forms of childhood tuberculosis.

Alexander Fleming

Scientist who in $1928$ discovered penicillin after observing that Penicillium mould inhibited bacterial growth on a culture plate.

Ernst Boris Chain and Howard Florey

Scientists who, along with colleagues, developed methods to purify penicillin and demonstrated its medical application.

Antibiotic Resistance

The ability of a bacterial strain to survive or multiply despite the presence of an antibiotic that would normally inhibit or kill it.

MDR-TB

Multidrug-resistant tuberculosis showing resistance to at least isoniazid and rifampicin, two essential first-line medicines.

XDR-TB

Extensively drug-resistant TB, defined as MDR/RR-TB that is additionally resistant to any fluoroquinolone and at least one Group A drug (bedaquiline or linezolid).

Microbiota

The community of microorganisms naturally residing in and on the human body, such as within the gut.

Probiotic

Live microorganisms that confer a measurable health benefit on the host when administered in adequate amounts.

Yoghurt Starter Cultures

Specific bacteria, commonly Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus, added to milk to ferment lactose into lactic acid.

Casein Coagulation

The process during yoghurt production where the accumulation of lactic acid decreases milk pH, causing milk proteins (mainly casein) to precipitate and form a soft gel.

Lag Phase

The initial period in a closed culture with little or no population increase, during which bacterial cells adapt to conditions and produce required enzymes.

Log (Exponential) Phase

The growth phase where bacteria divide rapidly at a nearly constant rate due to surplus nutrients and favourable conditions.

Stationary Phase

The growth phase where overall population size plateaus because the rate of cell division roughly balances the rate of cell death as nutrients decline and wastes accumulate.

Decline (Death) Phase

The phase in a closed culture where the number of viable cells decreases because cell death exceeds reproduction due to severe nutrient exhaustion and toxic waste buildup.

Optimum Temperature

The specific temperature at which a bacterial population achieves its highest growth rate.

Psychrophile

A cold-loving bacterium that grows best at relatively low temperatures.

Psychrotroph

A bacterium capable of growing at refrigeration temperatures, despite having a warmer optimum growth temperature.

Mesophile

A bacterium adapted to moderate temperatures, frequently having an optimum near human body temperature ($37^\circ\text{C}$).

Thermophile

A heat-loving bacterium adapted to thrive in warm or hot temperatures.

Acidophile

A bacterium that grows optimally in acidic environments with low pH values.

Alkaliphile

A bacterium that exhibits optimal growth in alkaline environments with high pH values.

Prokaryote

A single-celled organism that lacks both a membrane-bound nucleus and membrane-bound organelles.