Directed Mutation in Bacteria

by


    Jill Abery

Very occasionally an entrenched dogma within the scientific
establishment is challenged, not by a crank writing in green ink from a
private address, as Phillip Gething describes those offering new
theories from outside academia [1], but by reputable researchers with
papers even sometimes published in /Nature./ The reaction can be varied.
In the case of Rupert Sheldrake's theory of formative causation [2],
/Nature/ unpenned the Furies and declared his book fit for burning. In
the case of a French researcher's work which seemed to prove that there
was something behind homeopathy [3], /Nature/ sent in a team of
debunkers including a magician. In both cases /New Scientist/ was rather
more open-minded but both subjects have since dropped out of sight.

More recently /Nature/ has published a work which strikes at the roots
of modern Darwinism and raises the spectre of that old arch enemy,
Lamarckism [4]. This has not raised quite such a furore mainly, I
suspect, because those sufficiently roused to pen letters to scientific
journals on the subject feel that they can satisfactorily explain the
results without recourse to ideas of inheritance of acquired
characteristics, and as the experiments only deal with bacteria there is
always the let out that the results do not apply to higher organisms.
However, it is precisely because of studies of the mutation rates in
bacteria that biologists have come to believe that 'mutations arise
continuously and without any consideration for their utility'. This has
become the basic evolutionary doctrine of random variation upon which
the forces of natural selection can act.

In a recent experiment, Cairns/ et al/. studied strains of bacteria
which lacked the right genes to enable them to metabolise certain
sugars. These strains were grown on a medium containing sugars they
could metabolise; measurements of the rate of mutations which would
allow them to grow on media containing the other sugars showed that the
mutation rate was extremely small. Significantly, one example actually
required two separate mutations, neither of which was any use by itself.
Nevertheless, when the bacteria were grown on a medium containing only
the sugars they could not metabolise, within two weeks they had mutated
to be able to do so. The authors estimated the chances of this occurring
with the 'normal' mutation rates and wrote:

"That such events ever occur seems almost unbelievable,.... It is
difficult to imagine how bacteria are able to solve complex problems
like these - and do so without, at the same time, accumulating a large
number of neutral and deleterious mutations - unless they have access to
some reversible process of trial and error.... We describe here a few
experiments and some circumstantial evidence suggesting that bacteria
can choose which mutations they should produce."

It appears that molecular biology is no longer as reductionist as it
was; it is now accepted that in some genetic systems instability and
extreme variability can be switched on in conditions of stress. But
merely increased mutation rate, if still random, would lead to the
accumulation of vast numbers of deleterious mutations, for which there
is no evidence. The authors speculate about intra-cellular mechanisms
which could feed back information about the success or otherwise of
mutations and allow the cell to concentrate only on the advantageous
ones, but it has hitherto been sacrosanct in biology that there is no
mechanism for such feedback from the environment to the genome. Such
processes would 'in effect, provide a mechanism for the inheritance of
acquired characteristics'. It is ironic that scientists in the past have
been pilloried for daring to suggest such things [5,6].

Other biologists will not yet consider the effect seriously until there
is more proof, and a valid mechanism, and even then they are likely to
consider the phenomenon applies only to the relatively simple chemical
world of bacteria. A batch of letters to /Nature/ [7] all made great
effort to explain the heterodox results away. A further paper by another
researcher [8] which gave even more suggestive results for anticipatory
mutation, was again argued against in /Nature /[9] but Cairns had
counterarguments and an explanation for the 'vehement defence' of
orthodoxy his work had aroused [10]. He exhorted his readers to remember
that his critics are defending what is 'an essentially negative
assertion', that adaptation of an organism to its environment never
precedes the genetic changes for the adaptation. Although /Nature/ only
printed the critical letters, Cairns had been contacted by other
researchers with similar beliefs and in view of the fact that scientists
now know

    "that, in the processing of biological information, almost anything
    is possible.... it should not be difficult for an organism to devise
    a way of testing phenotype (newly adapted characters) before
    adopting any new genotype (heritable characters). "

Cairns sums up by saying:

    "It therefore seems almost perverse to maintain, as a matter of
    principle, that such a mechanism has never evolved."

However these results may eventually be explained, there is no doubt
that the purely mechanistic dogma of evolution by natural selection of
completely random mutations leaves much to be desired. The more
biologists discover about the complexity of living organisms the more
there is to explain. An alternative scenario could be that our present
era is one of relative stasis in which natural selection serves to keep
the /status quo/ and that evolution proceeded in catastrophic leaps at
times of chaotic change. Perhaps the potential for complex feedback
mechanisms between organisms and their drastically altered environment
lies largely dormant and comes into play only at such times, when some
means of very rapid adaptation is essential; means such as the
inheritance of acquired characteristics and reinforcement through
morphic resonance, of which we catch only glimpses at the present time.
Though such glimpses reveal a whole new way of thought for those with
the breadth of mind to accept them, the orthodox will continue to deny
them while they cling tenaciously to the fragile reassurance of a belief
in a non-catastrophic Universe.

*References*

1. /New Scientist/ 4.11.89, p. 73
2. See /Workshop/ 4:3, p. 18
3. /Nature/ *333*, p. 787
4. /Nature/ *335*, pp. 142-5
5. A. Koestler, /The Case of the Midwife Toad/
6. See /Workshop/ 4:1, pp. 11-12, on the work of Ted Steele and the
inheritance of acquired immunity.
7. /Nature/ *336*, pp. 525-7
8. /Genetics/, December 1988
9. /Nature/ *337*, pp. 119-20
10. /Nature/ *336*, pp. 527-8

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