ng, Sophie Desmonde, Patricia Dumazert, Antoine Jaquet, Julie Jesson, Valeriane Leroy, Karen Malateste, Elodie Rabourdin, Thierry Tiendrebeogo, ADERA, Isped & INSERM U1219, Bordeaux, France. Didier Koumavi Ekouevi, Jean-Claude Azani, Patrick Coffie, Abdoulaye Cissé, Guy Gnepa, Apollinaire Horo, Christian Kouadio, Boris Tchounga, PACCI, CHU Treichville, Abidjan, Côte d'Ivoire


1. Introduction {#s0005}
===============

Microgravity is a condition found to exist, when the small collision accelerations are not exceeding 10^−5^ to 10^−4^ × g of background level ([@b0005]). The bacterial cells experience microgravity when force of gravity acting upon them is opposed by another force. Microgravity is one of the conditions existing in space. Space flight was found to suppress the immune system in humans and animals, ([@b0120], [@b0130], [@b0150]) suggesting that risk of infectious diseases during spaceflight is high. Studies on changes experienced by bacteria under microgravity conditions during space flight are important in order to understand the behavior of microorganisms under microgravity. Spaceflight effects on the process of infectious diseases were investigated early at the level of host susceptibility, so present researches were carried to find the ability of bacteria to change their physiology and virulence which is important to decrease the risks to crew members during space flight ([@b0125]). It is difficult to study each and every bacterium during the space flights because of constraints faced in space crews. So high aspect rotating vessel (HARV), a ground based model had been utilized for performing experiments by mimicking microgravity condition.

Alterations in composition of oral and cutaneous microflora were observed in Vostok crew members after space flight. Also decrease in useful microorganisms and increase in pathogens were observed during space flight on Salyut and Mir orbital stations ([@b0010], [@b0070]). A variety of bacterial species were found to exhibit large population changes unde