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Bacterial genetics
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- University Of Leeds (UoL)
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BLGY1232 Bacterial GeneticsBacterial genetics
The study of heredity and the variation of inherited characteristics; vast majority are
haploid so genetics is relatively simple as no recessive mutations, lateral/horizontal
gene transfer is an important component of bacteria genetics
The genetic properties or features of an organism; as a domain of life contain
100,000s of different gene families and encode a diverse metabolism
Streptomyces and other actinobacteria have a secondary metabolism that is the
source of numerous chemotherapeutics including antibacterial, anticancer,
immunosuppressive, antihelmintic and antifungal agents The chemistry of this
secondary metabolism, the ‘parvome’, is structurally diverse and based on a number
of different backbone structures, e.g. polyketides, β-lactams, peptides and pyrroles
The natural function of many Streptomyces secondary metabolites is considered
to be as antibiotics that thwart the growth of competing microorganisms
Genetics
Understanding genetics allows one to investigate, predict, modify and understand
the molecular and cellular basis of phenotypes
Genetic reversion – a return to a prior state by a second mutation
Cyanobacteria
Fossil traces of cyanobacteria have been found from around 3.5 billion years ago
(b.y.a.)
Cyanobacteria (Greek: κυανόs [kyanós] = blue + bacterium) is a phylum (or
"division") of bacteria that obtain their energy through photosynthesis
Often still referred to as blue-green algae, although they are in fact bacteria
They are a major primary producer in the planetary ocean They are
photoautotrophs (from the Greek autos = self and trophe = nutrition) that produce
organic compounds from carbon dioxide as a carbon source using light as a source of
energy They also fix atmospheric nitrogen
, Their ability to perform oxygenic (plant-like) photosynthesis is thought to have
converted the early reducing atmosphere into an oxidizing one, which dramatically
changed the life forms on Earth
Bacteria
A prokaryote (2 domains) is an organism whose cells lack a true, membrane-
enclosed nucleus
Bacteria (also called eubacteria) are prokaryotes, but not all prokaryotes are bacteria
Some are Archaea (also called archaebacteria) that have eukaryotic-like features
in, for example, transcription and translation
Prokaryotes are arguably the most evolutionarily diverse group of free-living
organisms; however, only a few prokaryotic species have been manipulated
genetically much of what we know about ‘prokaryotic’ genetics is by
extrapolation from the study of a few model organisms e.g. E. coli, Salmonella and B.
subtilis, and inferred by genome comparison
Where did life originate?
Perhaps extreme environments at high temperatures; such as in hydrothermal vent
sites in, for example, the Sea of Cortés Vents ‘spew’ out H2S and FeS, reduced
chemicals that if oxidised produce energy
Prokaryotes in these vent have been found that use this energy to turn CO2 into CHO,
e.g.Hydrogen sulfide chemosynthesis - 6{CO2}+6{H2O}+3{H2S}→C6H12O6+3{H2SO4}
Such bacteria are called chemoautotrophs and can be primary producers
The ‘bacteria’ provide food for giant tube worms, grow up to eight feet in length and
have no mouth or gut When worms are juveniles, they have a primitive mouth
and gut through which the ‘bacteria ‘enter As the worm grows older, the mouth
and gut disappear, trapping the bacteria inside The tubes worms depend on
symbiotic relationship with bacteria that live inside them The bacteria, which may
make up half of a worm's body weight, turn oxygen, hydrogen sulfide, and carbon
dioxide into organic molecules, food shared with the worm The bright red color of
the plume results from haemoglobins have the ability to bind and transport oxygen
and/or hydrogen sulfide the plume provides essential nutrients to bacteria living
inside, as part of a symbiotic relationship It is believed that the communities of
shrimps and crabs have been found living around these giants feed by nibbling off
bits of the tube worms' red plumes
Extremophiles
Many extremophiles are archaea Not only do they survive and thrive in geysers
and black smokers, others are found in very cold habitats or in highly-saline, acidic,
or alkaline water
However, other archaea are mesophiles, and have been found in environments like
marshland, sewage, sea water and soil
Many methanogenic archaea are found in the digestive tracts of animals such as
ruminants, termites, and humans
As of 2007, no clear examples of archaeal pathogens are known, although a
relationship has been proposed between the presence of some methanogens and
human periodontal disease
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