Interestingly, models of bacterial evolution suggest HGT as a mechanism of adaptation into either symbiosis or parasitism [ 32 ] .

Modeling a few thousand generations of bacterial evolution in a few microenvironment.

This is mainly because of clusters of genes that remain well conserved during bacterial evolution [ 12].

The general trends of bacterial evolution indicate that bacteria started as free-living organisms.

However, it appears to have differentiated to several distinct orthologous groups only later in bacterial evolution.

Just as bacterial evolution had allowed microbes to develop resistance to penicillin, strains of S. aureus evolved to become resistant to methicillin.

Large deletions in other bacterial genomes Genome comparisons across other groups of related bacteria suggest that deletion events encompassing multiple loci are frequent in bacterial evolution.

This lack of any clear species concept in microbiology has led to some authors arguing that the term "species" is not useful when studying bacterial evolution.

Richard Lenski and his colleagues have been conducting a long-term experiment in bacterial evolution, one that has encompassed over 30,000 generations of bacteria going back over 20 years.

The new units are highly complex, and the chances of their being duplicated by bacterial evolution, even under forced draft, are too small to worry about.