Brock Biology of Microorganisms

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(b) Sample of water from 7 m in Lake Mahoney, British Columbia. The major organism is Amoebobacter purpureus. c) Phase-contrast photomicrograph of layers of purple sulfur bacteria from a small stratified lake in Michigan. The purple sulfur bacteria include Chromatium species (large rods) and Thiocystis (small cocci). PURPLE NONSULFUR BACTERIA Purple nonsulfur bacteria (Table 12.3) from organic compounds - most can grow as chemoorganotrophs in darkness, fermentative respiration – represses photosynthetic machinery They can use sulfide but at much lower concentration than the Purple Sulfur Bacteria CO 2 + H 2 S (electron donor) or also CO 2 + H 2 As they can use organics and also light, this gives them a competitive advantage. Nutrition: diverse substrates Most fix nitrogen Diverse group but all fall in the alpha or beta Proteobacteria Purple nonsulfur bacteria (see Table 12.3). Rhodopseudomonas acidophila; cells are about 4 µm long. Rhodobacter sphaeroides; cells are about 1.5 µm wide. 6
12.2 Concept Check Purple bacteria are anoxygenic phototrophs that grow phototrophically, obtaining carbon from CO 2 + H 2 S (purple sulfur bacteria) or organic compounds (purple nonsulfur bacteria). Purple nonsulfur bacteria are physiologically diverse and most can grow as chemoorganotrophs in darkness. The purple bacteria reside in the alpha, beta, and gamma subdivisions of the Proteobacteria. • What is meant by the term anoxygenic? • Give a major reason why photosynthesis in purple nonsulfur bacteria does not occur under aerobic conditions. • Can purple bacteria grow in the absence of light? 12.3 THE NITRIFYING BACTERIA p. 335 Chemolithotrophs are prokaryotes that oxidize inorganic electron donors and in many cases use CO 2 as their sole carbon source. NITROSIFYERS AND NITRIFYERS p.336 Nitrifying bacteria •Several reactions occur in the oxidation of inorganic nitrogen •compounds by chemolithotrophic nitrifying bacteria (Fig. 12.9). Occur in alpha, beta, gamma and delta Proteobacteria Sequential action. First: Ammonia oxidizers or Nitrosifyers (Nitroso - genus) ammonia ► hydroxylamine ► nitrite Nitrite oxidizers – or Nitrifying bacteria (esp. Nitrosomonas & Nitrosomonas Nitrite to nitrate Most are obligate aerobes. Yet grow with high ammonia e.g. sewage. A scourge to farmers – fertilizers ► soluble and leachable nitrates Membrane associated nitrification enzymes 7
Page 1 and 2: Michael Madigan • John Martinko B
Page 3 and 4: PROTEOBACTERIA • The Proteobacter
Page 5: Figure 12.4a Bright-field purple su
Page 9 and 10: 12.4 SULFUR- AND IRON-OXIDIZING BAC
Page 11 and 12: 12.5 Hydrogen-Oxidizing Bacteria So
Page 13 and 14: TWO PHYSIOLOGIES • Two classes ar
Page 15 and 16: Characteristics of Pseudomonads p.3
Page 17 and 18: Zymomonas p. 347 Sugar fermentation
Page 19 and 20: Figure 12.22 Neisseria and Chromoba
Page 22 and 23: Proteus mirabilis - swarms in conce
Page 24 and 25: 12.13 RICKETTSIAS p.347 •The rick
Page 26 and 27: Spirillum volutans Ancyclobacter da
Page 28 and 29: 12.15 Sheathed Proteobacteria: Spha
Page 30 and 31: 12.15-12.16 Concept Check Sheathed
Page 32 and 33: 12.18 Concept Check Sulfate- and su

Brock Biology of Microorganisms

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