ABSTRACT

Members of the gram-negative bacterial genus Pseudomonas are ubiquitous in soil and water ecosystems [1]. Their genetic exibility, versatility in optimizing the usage of a vast array of organic and inorganic compounds, and innate capability to survive under diverse, often trying, environmental conditions are the key factors behind their successful inhabitation of most environmental niches found on our planet [2]. From the point of view of mankind, this genus is intriguing indeed. On the one hand, the ability of Pseudomonas to produce an arsenal of degradative factors makes it one of the most feared pathogens of plants and animals [3,4]. On the other hand, this same feature,

Introduction .................................................................................................................................... 321 Taxonomy....................................................................................................................................... 322 Life of Pseudomonas ..................................................................................................................... 323

Cellular Characteristics ............................................................................................................. 323 Physiology and Metabolism ...................................................................................................... 323 Habitat ....................................................................................................................................... 324 Laboratory Culture of Pseudomonas ........................................................................................ 325 Control of Gene Expression ...................................................................................................... 325

Quorum Sensing ................................................................................................................... 325 Two-Component Systems ..................................................................................................... 325 Sigma Factors ....................................................................................................................... 325 Other Transcriptional Regulators ......................................................................................... 326 Post-Transcriptional Regulation ........................................................................................... 327

Examples of Prominent Pseudomonas Species ............................................................................. 327 Pathogenesis of P. aeruginosa ................................................................................................... 327

General Pathogenicity Attributes .......................................................................................... 327 P. aeruginosa Pathogenesis in the CF Lung Environment ................................................... 329 Infrequent Pseudomonas Species as Human Pathogens ....................................................... 330

Phytopathogen P. syringae ........................................................................................................ 330 Mechanism of Spread ........................................................................................................... 330 Pathogenic Properties and Genes ......................................................................................... 330

Bioremediation by P. putida ...................................................................................................... 331 Metabolic Potential for Bioremediation ............................................................................... 331 P. putida in the Rhizosphere ................................................................................................. 331

P. fluorescens, the Phyto-Benefactor ......................................................................................... 332 Fitness to Exist in the Rhizosphere ...................................................................................... 332 Regulatory Mechanisms ....................................................................................................... 332 Role of Pf-5 in Biocontrol .................................................................................................... 332

Conclusion ..................................................................................................................................... 332 Acknowledgments .......................................................................................................................... 333 References ...................................................................................................................................... 333

combined with biochemical prociency for metabolizing toxic hydrocarbons and other compounds, has rendered it one of the most prized organisms for bioremediation of recalcitrant wastes [5-7]. This chapter briey describes the current taxonomical position and general features of Pseudomonas. This discussion is followed by a section describing some of the prominent members of this genus, and their respective roles in pathogenesis, bioremediation, and plant symbiosis.