anaerobe - organism that wants very little or no oxygen
autotrophs - organisms that need no preformed organic foods
bacterial endospores - see endospores
auxostat - A device that uses the rate of feeding to control a state variable in continuous culture is termed an auxostat. The organisms establish their own dilution rate.
bacteriophage - virus (phage) that infects a bacterium
chemostat - constant volume continuous cultivation with fixed flow rate; dilution rate = F/V
chemotrophs - organisms that derive energy from inorganic reactions
constitutive - enzyme always synthesized and ready
dilution rate - feed rate to vessel divided by volume of vessel
endospore - seed-like structure; formed to preserve life when conditions turn bad
eukaryotic - cell has nucleus; divides through mitosis
facultative - prefers but not absolute, e.g., facultative anaerobe
heterotrophs - organisms that must have carbon-energy compounds
inducible - enzyme not synthesized or activated until needed
obligate - absolute requirement, e.g., obligate aerobe
pathogens - organisms that cause disease
phage - viruses for microorganisms
photosynthesis - All living cells synthesize ATP, but only green plants and a few microorganisms can drive biochemical reactions to form ATP with radiant energy through the process of photosynthesis. The number per cell of membrane-surrounded organelles called chloroplasts varies with species and environmental conditions. In higher plants numerous chloroplasts are found in each cell of the mesophyll tissue of leaves, while an algal cell may contain a single chloroplast. A chloroplast has a sandwich of many layers alternating between pigments and enzymatic proteins such that electromagnetic excitation from light becomes chemical bond energy. Prokaryotic organisms - bacteria and cyanobacteria (formerly called blue-green algae) - do not possess chloroplasts. Instead their photosynthetic systems are associated with the cell membrane or with lamellar structures located in organelles known as chromatophores. Chromatophores, unlike chloroplasts, are not surrounded by a membrane.
All photosynthetic organisms contain one or more of the group of green pigments called chlorophylls. In addition many contain accessory pigments that impart characteristic colors to the cells.
The net result of photosynthesis is to reduce carbon dioxide to form carbohydrates. A key intermediate is phosphoglyceric acid, and various simple sugars are reacted and disproportionated as the carbon from carbon dioxide is incorporated.
prokaryotic - no organized nucleus
protozoa - tiny animals; most feed on microorganisms
recycle More dense cell concentrations can be achieved by separating cells from the effluent and recycling them to the fermenter. This has been standard practice for many years in biological waste treatment where dilute feed streams result in slow growth of the culture. Producing cell flocs that are collected easily by sedimentation is aided by recycling those cells that do settle. This is a selective advantage that may allow them to dominate. Industrial fermentations can afford more expense than can waste treatment, and centrifuges for collecting cells are not uncommon. Recycle of yeast cells can lower the fermentation time for ethanol significantly.
yeast - eukaryotic organisms larger than most bacteria, commonly divides by forming a bud that separates leaving a scar. When the outside of a yeast cell has too many scars, reproduction ceases.
While the well-known chemostat is stable and simple for investigating continuous cultivation at low to moderate dilution rates, an auxostat tends to be much more stable at high dilution rates. Population selection pressures in an auxostat lead to cultures that grow rapidly. Practical applications include high-rate propagation, destruction of wastes with control at a concentration for maximum rate, open culturing because potential contaminating organisms cannot adapt before washing out, and operation of processes that benefit from careful balance of the ratios of nutrient concentrations.