Microbiology Lecture: Bacterial Morphology and Growth

VOCABULARY flashcards covering bacterial cell structures, transport mechanisms, growth phases, and environmental requirements based on the lecture transcript.

Binary fission

The process of asexual reproduction in bacteria where one cell increases its volume, duplicates its DNA, and splits into two daughter cells.

Psychrotrophs

Microbes that grow between $20$ and $30$ degrees Celsius and are important in the spoilage of refrigerated foods.

Lag phase

The first stage of the bacterial growth curve during which cells are synthesizing proteins and duplicating DNA but not yet increasing in number.

Facultative anaerobes

Organisms that grow better in the presence of oxygen using aerobic respiration but can also grow without it through fermentation or anaerobic respiration.

Superoxide dismutase

An enzyme that neutralizes toxic superoxide radicals, allowing organisms to live in the presence of oxygen.

pH Range for Bacteria

Every bacterium has a specific, narrow pH range within which it can survive.

Optimum pH

There is a specific pH level at which a bacterium grows best, often around neutral (pH 7).

Neutrophiles

Bacteria that thrive in neutral pH, typically between 5 and 8, with an optimum around 7.

Acidophiles

Bacteria that grow best in acidic environments with a pH below 5.5; some can survive at a pH of 0.

Alkaliphiles

Bacteria that grow best at a basic pH, specifically above 8.5, with some species able to survive up to pH 14.

Plasmolysis

Occurs when bacteria are in a hypertonic environment, causing water to leave the cell and leading to cell shrinkage.

Osmotic Lysis

Occurs when the solute concentration is higher inside the cell, causing water to enter and potentially burst the cell.

Halotolerance

The ability of certain microorganisms to withstand high salt concentrations without requiring them for growth.

Halophiles

Salt-loving organisms that require high salt concentrations to survive.

Prokaryotic Nutrient Requirements

Essential elements required to build macromolecules including DNA, RNA, carbohydrates, proteins, and fats.

Autotrophs

Organisms that use inorganic carbon, specifically in the form of carbon dioxide (CO2) gas.

Heterotrophs

Organisms that cannot use inorganic carbon and must use organic compounds like glucose.

Phototrophs

Organisms that derive energy from sunlight.

Chemotrophs

Organisms that derive energy from chemical compounds.

Fastidious Organisms

Microbes with complicated nutritional requirements that are difficult to replicate in a laboratory.

Complex Media

Contains a variety of ingredients where the exact chemical composition varies batch to batch (e.g., yeast extract, beef extract).

Chemically Defined Media

Prepared by weighing every specific ingredient; the precise amount of every chemical is known, used for highly controlled experiments.

Selective Media

Inhibits growth of unwanted microorganisms while allowing target microbes to grow.

Thayer-Martin Agar

Used to isolate Neisseria gonorrhoeae from genital swabs by inhibiting the normal microbiome.

Macombi Agar

Isolates gram-negative bacteria, contains dyes that inhibit gram-positive growth.

Differential Media

Contains substances that bacteria act upon to produce a recognizable change.

Blood Agar

Contains $5\%$ sheep's blood; differentiates bacteria based on their ability to produce hemolysin.

Beta Hemolysis

Complete lysis of red blood cells, resulting in a transparent area around the growth.

Alpha Hemolysis

Partial lysis producing a greenish appearance.

Gamma Hemolysis

No hemolysis occurs.

Capnophiles

Require high concentrations of $CO_2$ for growth.

Microaerophiles

Require lower concentrations of oxygen ($O_2$) than present in the atmosphere.

Anaerobes

Organisms that die in the presence of oxygen.

Direct Microscopic Count

Counts bacteria under a microscope to estimate total population without distinguishing living from dead cells.

Viable Plate Count

Counts only live bacteria that form colonies on solid agar.

Membrane Filtration

Technique used for samples with low bacterial concentrations, trapping bacteria on a membrane.

Turbidity

Measurement of broth cloudiness using a spectrophotometer to estimate bacterial concentration.

Total Weight (Biomass)

Method of measuring bacterial mass after filtering, drying, and weighing.