GLOSSARY - Bioaugmentation for Groundwater Remediation - page 373

Reductase ‐ An enzyme catalyzing a reducing reaction.

Reduction ‐ Transfer of electrons to a compound such as oxygen; occurs when another
compound is oxidized.

Reductive dechlorination (hydrogenolysis) ‐ Reaction involving removal of one or more
chlorine atoms from an organic compound and their replacement with hydrogen atoms.
A subset of reductive dehalogenation. Key reaction for anaerobic degradation of chlorinated
solvents.

Reductive dehalogenation ‐ The process by which a halogen atom (e.g., chlorine or bromine)
is replaced on an organic compound with a hydrogen atom. The reactions result in the net
addition of two electrons to the organic compound.

Remediation ‐ Cleanup or other methods used to remove or contain contamination.

Rhizosphere ‐ The soil on and near the roots of plants. This soil zone, directly influenced by
root secretions, is teeming with microorganisms that feed on sloughed-off plant cells and the
compounds released by roots.

Ribonucleic acid (RNA) ‐ One of the three major macromolecules (along with DNA and
proteins) essential for all known forms of life. Like DNA, RNA is made up of a long chain of
nucleotides, but unlike DNA, RNA contains the sugar ribose (instead of deoxyribose) and
contains the nucleobase uracil (instead of thymine). RNA molecules are used to catalyze
biological reactions, control gene expression, and synthesize proteins. There are three main
types of RNA: messenger RNA (which directs the assembly of proteins on ribosomes), transfer
RNA (which delivers amino acids to the ribosome), and ribosomal (which links amino acids
together to form proteins).

Ribosome ‐ A component of cells that synthesizes protein chains. Ribosomes are the location
for the process known as translation, in which the ribosome translates the genetic information
from the messenger RNA (mRNA) by binding to an mRNA and using it as a template for
determining the correct sequence of amino acids.

Saturated zone ‐ Part of the subsurface that is beneath the water table and in which the pores
are filled with water.

Seepage velocity ‐ The average pore water velocity. Since groundwater flow actually occurs
only through interconnected pores and not through the entire subsurface volume, as assumed in
calculating the Darcy velocity (V), the seepage velocity (V S ) is equal to the Darcy velocity
divided by the porosity (n), or V S ¼

V/n.

Semi-passive treatment ‐ In situ bioremediation approach in which amendments are added to
the subsurface intermittently (i.e., at intervals of a few weeks to a few months). Generally,
water soluble compounds serve as the electron donor. The accumulation of biomass can also
serve as a longer-term source of electron donors.

Sequencing ‐ Generally refers to DNA sequencing, i.e., the process of determining the

nucleotide order of a given DNA fragment.