Microbes and Metabolism - Environmental Biotechnology: Theory and Application - page 20

Figure2.4 Nucleicacids
the cell which sometimes requires specific carrier proteins to allow penetration
across the cell membrane. Once entered, the enzymes must be present to catalyse
all the reactions in the pathway responsible for degradation, or catabolism. The
information for this metabolic capability is encoded in the DNA. The full genetic
information is described as the genome and can be a single circular piece of DNA
as in bacteria, or may be linear and fragmented into chromosomes as in higher
animals and plants.
Additionally, many bacteria carry plasmids, which are much smaller pieces
of DNA, also circular and self-replicating. These are vitally important in the
context of environmental biotechnology in that they frequently carry the genes
for degradative pathways. Many of these plasmids may move between different
bacteria where they replicate, thus making the metabolic capability they carry
transferable. Bacteria show great promiscuity with respect to sharing their DNA.