Classification of Micro-organisms and Bacterial Cell Structure

Vocabulary flashcards focusing on key classification methods, cellular structures, and cell wall differences between Gram-positive and Gram-negative bacteria.

Microbiology

The study of microorganisms, including unicellular prokaryotes, multicellular eukaryotes, and non-cellular viruses.

Quorum Sensing

A cell-cell communication process used by bacteria to regulate gene transcription and monitor their own cell population density.

Autoinducers

Diffusible signal molecules, also known as pheromones, produced during quorum sensing that enable a bacterium to monitor cell density.

Plasmids

Small and specialized genetic elements capable of self-replication that can carry genetic information such as antibiotic resistance genes.

Mycoplasmas

Parasitic prokaryotes that have lost the ability to form a cell wall and instead incorporate substantial host cholesterol into their cell membrane.

Gram Stain

A staining procedure invented by Hans Christian Gram that divides most bacteria into Gram-positive and Gram-negative groups based on fundamental cell surface differences.

Psychrophiles

Bacteria classified by their temperature preference as cold-loving.

Mesophiles

Bacteria classified by their temperature preference as moderate heat-loving.

Thermophiles

Bacteria classified by their temperature preference as high heat-loving.

Nucleoid

The region in a prokaryotic cell where DNA is packaged without a surrounding nuclear membrane, visible under a light microscope on stained slides.

Peptidoglycan

Also referred to as murein or mucopeptide, a cell wall layer that gives the cell wall high tensile strength to withstand osmotic pressure.

Lipopolysaccharide (LPS)

A major component of the Gram-negative bacterial outer membrane that is responsible for non-specific endotoxin activity.

Gram-Positive Bacteria

Bacteria possessing large bundles of peptidoglycan in their cell wall that retain the crystal violet-iodine complex and appear purple under a microscope.

Gram-Negative Bacteria

Bacteria with fewer peptidoglycan bundles that lose the primary crystal violet-iodine complex during decolorization and stain red with counterstains like safranin, neutral red, or dilute carbol fuchsin.

Gram-Negative Bacterial Cell Wall Structure

The multi-layered envelope of Gram-negative bacteria containing an outer membrane with lipopolysaccharides and porins, a periplasmic space with murein lipoprotein, and an inner cytoplasmic membrane.

Gram-Positive vs. Gram-Negative Cell Wall Comparison

Structural differences illustrating that Gram-positive bacteria contain teichoic acid, lipoteichoic acid, and thick peptidoglycan, whereas Gram-negative bacteria possess lipopolysaccharides, an outer membrane, lipoproteins, and thin peptidoglycan.