General and Applied Aspects of Halophilic Microorganisms

Abstract

During recent years the subject of extreme environments and extremophiles has become a central topic in modern Biology. The capability of some microorganisms to withstand, and often prefer, the harsh conditions found in such environments is helping to define the physicho-chemicallimits of life and in consequence its essential nature. Halophiles are one of the most representative types of extremophiles, requiring high concentrations of inorganic salts, mostly sodium chloride, to grow and survive. They inhabit hypersaline environments, the distribution and abundance of which dur ing geological eras are attested by the vast amounts of evaporite rocks present in the Earth crust and by their role in the generation of petroleum deposits. The corditions of high osmolarity and ionic strength that are concomitant with concentrated salt solutions challenge the stability of lipid bilayers and the structure of proteins forcing halophilic microbes to develop specialized molecules and physiological me;;hanisms to cope with this environmental stress. Even so, halophilism is a widespread trait in the microbial world. All the major groups of eucaryotic microbes, two groups of archaeobacteria and most phylogenetic branches of eubacteria have halophilic representatives. Therefore, the study of halophilic microorganisms is indeed a highly heterogeneous and extense topic. The present volume contains the contributions to the FEMS-NATO Advanced Research Workshop on "General and Applied Aspects of Halophilic Microorganisms" held at Alicante, Spain, September 17-22, 1989. At this meeting 46 invited speakers and 51 other participants presented their latest results through lectures and posters dealing with this diverse subject. I think we succeeded in getting a remarkably comprehensive view of the state of the art in the field. Obviously there were some areas that had to be treated shallowly, for example, the biophysics of the halobacterial retinal proteins, which has become a vast and highly specialized field with regular and frequent meetings dedicated specifically to it. On the other hand the spectacular ad vances in the field of haloadaptation and the molecular biology of halo bacteria (Sessions 2 and 4) have been widely covered. The rapid progress in these areas make them particularly appropiate for revision in a meeting such as this. As editor of the book I have to thank the authors for their contributions, the extremely high standard of which made my job very simple. I am very grateful to both NATO and the Federation of European Microbiological Societies (FEMS) for their sponsorship. Without the joint support from both parties this meeting could not have been held. Other organizations made substantial contributions to financing the meeting, v particularly the Spanish Ministry of Education and Science and the Valencian Government (Generalitat). All the staff and students of the Department of Molecular Genetics and Microbiology, University of Alicante worked hard and long helping in the organization of the meeting and I am very grateful to all of them. Finally a special acknowledgment is required of the invaluable contribution made by Kathleen Hernandez, the secretary of our Department, to both the organization of the meeting and the typing and preparation of this book, thank you.