London, Jan 4 (IANS): It's not only bigger animals that have intricate courtship. Even single-cell organisms so tiny that millions can fit into the eye of a needle love to mate. What you need is a powerful microscope to see this!

Researchers from the University of Bristol have observed mating for the first time in the microbes responsible for African sleeping sickness. This tropical disease is caused by trypanosomes - single-celled parasites that are found in the blood of those afflicted.

The researchers were able to see what the trypanosomes were getting up to inside the tsetse flies (large biting flies) that carry the disease by using fluorescent markers.

“We saw these tiny microbes twirling and gyrating together before joining up into one hybrid cell. To tell which was which, individual trypanosomes were tagged with different colours, with the result that the hybrid cells had both colours,” said professor Wendy Gibson who led the research.

“These results suggest that sex is not an optional or rare part of this microbe's life cycle, but probably happens every time two different trypanosomes find themselves together in the same tsetse fly,” he added.

Sex matters for microbes because it enables genes to be swapped between different strains, leading to new combinations of genes.

In the case of disease-causing microbes like the trypanosome, sex can potentially lead to a lot of harmful genes being combined in one strain, said the study that appeared in the journal "Current Biology".

This research would also help scientists understand how new strains of disease-causing microbes arise and how characteristics such as drug resistance get spread between different strains, said the study.