In 1995, the first bacterial genomes were
sequenced
First bacterial genome to be
sequenced: H. influenzae
Average protein coding content of a
bacterial genome is 40 to 97 %
A typical bacterial genome is around 5
million bp, encodes about 5000 proteins
Largest genome is Sorangium cellulosum strain So0157-2, has 14,782,125 bp, contains
11,599 genes
Smallest genome is Candidatus Nasuia deltocephalinicola strain NAS-ALF; has 112,091bp, codes for only
137 proteins
The GC content of the finished bacterial
genomes ranges from a bit less than 15% to about 85%
Extremophiles: thermotolerant,
psychrotolerant, and psychrotrophic bacteria
Members
of a species are not necessarily “equal” or even similar, in terms of their
(protein-coding) gene content
Depending
on the species, the variation in gene content and genome size can be quite
considerable, with some pan-genomes, like E.
coli, being very “open”; other pan-genomes, such as that for Bacillus anthracis, contain very
few extra genes, and can be considered “closed”.
Species can vary by more than a megabase
e.g.Haemophilus influenza HK1212 (1.0 mb) versus F3047 (2.0 mb)
Burkholderia
pseudomallei THE (6.3 mb) versus
MSHR520 (7.6 mb)
Core gene families :Families
with at least one member in at least of 95% of genomes
Serratia symbiotica str. Cinara
cedri has a protein-coding
density of 38%, is an insect co-symbiont, having 58 pseudogenes.
Redundancy arise from gene duplications
Repeat sequences and parasitic DNA that
seem to bear no function to the organism.
Bacterial genomes are not always evolving
towards optimal efficiency
Increased number of tRNAs and rRNAs is
correlated with a faster growth rate
Insertions and deletions arise from
recombination events
All bacterial genomes have at least one
copy of the 23S, 16S and 5S rRNA genes.
Genetic code allows for 62 possible
anticodons for tRNAs, but since these have to cover only 20 essential amino
acids, the theoretical minimum for a genome would be 20 tRNA genes.
The number of anticodons identified per
genome has not exceeded 47 (out of 62 possible), and averages between 33 and 35
Bacteria control mobile elements through post-segregation
killing systems