Sequence divergence .589 Incidence and level of competence in natural isolates.589 Physiological effects of DNA uptake .590 Environmental Level 590 DEDUCTIVE EVIDENCE FOR BACTERIAL TRANSFORMATION. 590 BIOLOGICAL FUNCTIONS OF DNA UPTAKE OTHER THAN GENE ACQUISITION.591 Regulation of Gene Expression.591 Protection of Cells against Bacteriophages .592 Supply with Nutrients. 592 DNA Repair.592 CONCLUSIONS AND PERSPECTIVES. 592 ACKNOWLEDGMENTS .59 REFERENCES.593 LORENZ AND WACKERNAGEL TABLE 1. Naturally transformable prokaryotic speciesa Species isolated from terrestrial Transformation frequency or aquatic habitats (chromosomal marker Reference(s) transformants/viable cell) Photolithotrophic Agmenellum quadruplicatum Anacystis nidulans Chlorobium limicola Nostoc muscorum Synechocystis sp. strain 6803 Synechocystis sp. strain OL50 Chemolithotrophic Thiobacillus thioparus Thiobacillus sp. strain Y Heterotrophic Achromobacter spp. Acinetobacter calcoaceticus Azotobacter vinelandii Bacillus subtilis Bacillus licheniformis Deinococcus (Micrococcus) radiodurans Lactobacillus lactis Mycobacterium smegmatis Pseudomonas stutzeri (and related species) Rhizobium meliloti Streptomyces spp. Thermoactinomyces vulgaris Thermus thermophilus Thermus flavus Thermus caldophilus Thermus aquaticus Vibrio sp. strain D19 Vibrio sp. strain WJT-1Cd Vibrio parahaemolyticus Methylotrophic Methylobacterium organophilum Archaebacteria Methanobacterium thermoautotrophicum Methanococcus voltae Clinical isolates of pathogenic species Campylobacter jejuni Campylobacter coli Haemophilus influenzae Haemophilus parainfluenzae Helicobacter pylori Moraxella spp. Neisseria gonorrhoeae Neisseria meningitidis Staphylococcus aureus Streptococcus pneumoniae Streptococcus sanguis Streptococcus mutans 4.