Study GuideMicrobiology–The Bacteria1.Gram-Negative Rods and CocciGram-negative bacteria include many different shapes and lifestyles. Some live freely in nature, somehelp plants and animals, and others can cause disease. Let’s explore the major groups step by step.1.1Bdellovibrios–Bacteria That Hunt Other BacteriaBdellovibrios areaerobic, Gram-negative, curved rod-shaped bacteriawith a very unusuallifestyle. Instead of living on nutrients in the environment, theyprey on other bacteria.The bdellovibrio attaches to another bacterium, spins, anddrills a hole through the host’s cell wall.It then enters the space between the cell wall and the plasma membrane. Once inside, it takes controlof the host’s cell machinery and grows. This process eventuallykills the host bacterium.The best-studied species in this group isBdellovibrio bacteriovorus, which has a distinctivecomma-like shape.1.2Pseudomonads–Common and Versatile BacteriaPseudomonads areaerobic, Gram-negative rodsthat move usingpolar flagella. There aremorethan 30 speciesin this group.One well-known species,Pseudomonas fluorescens, produces ayellow-green pigment. Anotherimportant species,Pseudomonas aeruginosa, is medically significant because it can causeurinarytract infectionsandinfections in burned tissue.1.3Azotobacter and Rhizobium–Nitrogen FixersSpecies ofAzotobacterandRhizobiumare extremely important because they canfix nitrogenfromthe atmosphere.•Azotobacterlives freely in the soil.•Rhizobiumlives on the roots oflegume plants.Preview Mode
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