Genetics of Selected Marine Bacteria

Marine bacteria are usually described as those bacteria
which grow optimally in sea water. Their complex requirements
for specific ions (sodium, potassium and magnesium)
have been used to differentiate marine from terrigenous
bacteria. These requirements, however, vary at the gene level
through mutation. Both spontaneous and induced (ultraviolet
light) mutations to loss of the ion requirement were observed.
Spontaneous frequencies were low (below 10^-6); induced frequencies,
high (10^-1 to 10^-8). Back mutations were noticed.
A stepwise mechanism was postulated for the mechanism of the
mutation involved in the appearance of ion independent
bacteria in a population of cells. Genetic analysis of the mechanism by which variations
in ion requirements occurred included determination of base
ratios and of transformation frequencies. The base ratios
of mutant and parent bacteria were similar enough and the
transformation frequencies high enough (10^-3 to 10^-5) to
show a close relationship between the two types of bacteria. This similarity indicated that, although the genome of
marine bacteria, which clearly controls the requirement
for specific ions from the values of mutation frequencies,
is altered by the action of ultraviolet light, the change
was not observable by the methods used. The change could
have been induced on the gene level to effect the synthesis
of structural or functional proteins (enzymes).