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There is a process whereby unrelated (or related) bacteria, on close approach, can become connected by a tiny conjugation tube. A small ring of genetic material can then pass through the tube from one cell to the other. The receiving cell may or may not have firewall protection (see CRISPR or other protective measures like restriction enzyme endonucleases) against such incoming foreign genetic code. The recipient cells do not always have adequate protection and there are some well-known examples of what can then occur.

E. coli is a normal component of human intestines and dairy animal intestines. In the past this bacterium was not known to cause disease although nobody wanted such contaminating material in one’s food or water. Nevertheless, it was not a huge problem if there was some contamination from sewage or farm run-off. However, in 1982 there were some terrible cases where people died after consuming food or water contaminated with E. coli. Scientists discovered a new strain of the bacterium (E. coli 0157:H7) which possessed the Shiga toxin from the dysentery bacterium Shigella dysenteriae. Apparently, some E. coli cells had become contaminated with the Shiga toxin through the conjugation process.

More alarming are cases of conjugation in hospitals. In 1961 the first superbug appeared in a hospital in the United States. Methicillin resistant Staphlococcus aureus (MRSA), a much feared bacterium, is presumed also to have appeared through the conjugation process. Other alarming stories of bacterial resistance to antibiotics continue to appear.

Many people think that antibiotic resistance is an evolutionary process, or a case of favourable mutations developing which promote the success of the bacterium. It is no such thing. The passing of a plasmid involves information that is already available and able to be passed from one bacterium to another if they come into close contact (as for example happens in hospitals). And we see from the case of bacteria striving to eliminate such incoming genetic code as by the CRISPR system, for example, that this conjugation is not a process that is particularly favourable to the recipient bacterium. None of these events is the raw material for upward evolution.

Related Terms

  • Sexual Reproduction
  • CRISPR (Clustered Regularly Interspaced Palindromic Repeats)