SIMPLE LIFE 



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processes with the exchange of hereditary materials 

 exist in some species. 



Occurrence: widely distributed in land, water, and 

 air; many are parasites of plants and animals and 

 others are saprophytes, generally involved in the 

 process of decay; some are only in oxygen-free con- 

 ditions but most require oxygen; more than 1000 

 species. 



The bacteria are an ecologically diverse assem- 

 blage of organisms that live in moist to aquatic media. 

 They are widely distributed in air, water, and soil 

 and within and upon organisms. However, both as a 

 group and often as individual species, owing to their 

 ability to disperse via air and water currents, they 

 are cosmopolitan. Their ecology may be examined in 

 terms of their nutrition and physiology. Many 

 species require only inorganic materials and photo- 

 synthetic or chemosynthetic processes solve their 

 nutritional needs. In photosynthesis, oxygen never is 

 involved; e.g., certain sulfur bacteria use hydrogen 

 sulfide, sulfur, or thiosulfate with carbon dioxide, in 

 the presence of light, to form simple sugar (actually 

 cell materials in the proportion CH,©). The other 

 species require simple to complex organic compounds 

 which they gain by loose to rigid saprophytic and 

 parasitic behaviors and functions. Perhaps more 

 remarkable yet, many species can adjust their meta- 

 bolic needs to a variety of environments, some in- 

 dividuals running the gamut of autotrophic and 

 heterotrophic nutrition types. 



Further indication of metabolic plasticity is found 

 in their reaction to oxygen in their environment. 

 Some bacteria can live in situations ranging from 

 no oxygen to high oxygen content. Others rigidly 

 require the presence or absence of oxygen. 



Nutritional activities allow a convenient appraisal 

 of the most significant activities. Some bacteria, such 

 as those in the soil, ocean oozes, and surface waters, 

 are extremely important geomorphic agents. With 

 certain blue-green algae and fungi they accomplish 

 most of the transformation of organic matter to sedi- 

 mentary rock deposits. Most are extremely import- 

 ant in generating carbon dioxide into the atmos- 

 phere. They are prime oxidation agents in biogeo- 

 chemical cycles, those using oxygen to change am- 

 monia to nitrite and nitrite to nitrate (nitrifying 

 bacteria); hydrogen to water; sulfide to sulfur, sulfur 

 to thiosulfate, and thiosulfate to sulfate; and ferrous 

 iron to ferric iron; all processes involved in decom- 



posing or transforming compounds and in cycling 

 protoplasmic elements to plants. Also, the above re- 

 actions may be reversed by other bacteria (e.g., ni- 

 trate to nitrogen by denitrifying bacteria). In addi- 

 tion, certain species gain energy by regularly 

 simplifying a variety of organic compounds by 

 fermentation. Finally, are their close relationship 

 with other organisms. For example, they are bene- 

 ficial to plants of the pea family (in forming root 

 nodules, bacteria enable the plants to use atmos- 

 pheric nitrogen in a process called nitrogen fixa- 

 tion) and to hoofed mammals (stomach-inhabiting 

 bacteria enable digestion and fermentation of plants 

 otherwise indigestible). However, many cause plant 

 and animal diseases. Bacterial agents of human 

 disease cause plague, cholera, whooping cough, 

 dysentery, tuberculosis, scarlet fever, tularemia, 

 pneumonia, diptheria, syphilis, and gonorrhoea. Yet, 

 most bacteria are beneficial. For example, they al- 

 low man to preserve food by pickling and fodder by 

 ensilage; to produce vinegar; to dispose of sewage; 

 to manufacture a variety of sour milk products; to 

 obtain food from plants (most plants could not ob- 

 tain their nutrients without bacterial decomposition 

 and transformation of pre-existing organic com- 

 pounds); to prepare various alcoholic beverages; to 

 produce antibiotics (e.g., aureomycin, streptomycin, 

 and chloramphenicol), vitamins, and enzymes; and, 

 perhaps most important, to learn about the funda- 

 mental workings of life itself. 



CYANOPHYTA (Blue-green Algae) 



Diagnosis: protoplasmic organization; some are 

 solitary and cell-like, but most colonial or simple 

 "multicellular"; most are sheathed by a jelly-like 

 material; solitary species are nonmotile and free- 

 living or live upon objects, generally fixed and spheri- 

 cal or globular; colonial forms are "one cell" thick 

 and flat, spherical and hollow, massive and cubical, 

 or formless; "multicellular" types are filamentous 

 (thread-like) in the form of simple bead-like or spiral 

 threads or of branching threads; some filamentous 

 forms are colonial rather than multicellular; no indi- 

 cation that tissue-like material is formed (Figure 8.2). 



Structure: individuals distinct or in a common 

 jelly-like mass; without a distinct central body 

 (nucleus) surrounded by a typical nuclear mem- 

 brane, probably no membrane of any kind; chloro- 

 phyll and pigments not in chlorophyll-containing 



