24 ] The Classification of Lower Organisms 



Spirillum includes the typical spirals, lophotrichous, a small number of species of 

 harmless saprophytes in foul waters. 



Thiospira includes large lophotrichous spirals, colorless, containing granules of 

 sulfur. They are believed to live by chemosynthesis. 



Family 12. Acetobacteriacea [Acetobacteriaceae] Bergey, Breed, and Murray 

 1938. As gross objects, growths of Acetobacter aceti Beijerinck have been known since 

 prehistoric times. With included yeasts they constitute mother of vinegar (the old 

 names Mycoderma mesentericum Persoon, Ulvina aceti Kiitzing, and Umbina aceti 

 Nageli designated the combination of bacteria and yeasts, and it seems proper to 

 reject them). Free-swimming cells with polar flagella have been observed; ordinarily 

 the cells appear as rods in chains, heavily encapsulated, or as involution forms. 

 The organic food required by Acetobacter is alternatively alcohol, which is oxidized 

 to acetic acid, or acetic acid, which is oxidized to carbon dioxide and water. These 

 processes are strictly aerobic: to make vinegar, one exposes wine to air; to preserve 

 it, one seals the vessels. 



Family 13. Nitrobacteriacea [Nitrobacteriaceae] Buchanan in Jour. Bact. 2: 349 

 (1917). Organisms oxidizing the simplest organic compounds; or facultatively capa- 

 ble of chemosynthesis; or living strictly by chemosynthesis and strictly aerobic: mostly 

 Gram negative monotrichous or atrichous rods. 



Methanomonas is capable of oxidizing methane; Carboxidomonas of oxidizing 

 carbon monoxide; Hydrogenomonas, of oxidizing elemental hydrogen. Thiobacillus 

 includes organisms which oxidize hydrogen sulfide or elemental sulfur. 



Winogradsky had discovered chemosynthesis in the course of studies of Beggiatoa 

 and other sulfur-oxidizing organisms before he undertook to isolate bacteria which 

 cause nitrification, that is, the natural production of nitrates in soil and waters. 

 He achieved success (1890) by inoculating, with soil or sewage, media which con- 

 tained salts of ammonia but no food; he saw the nitrifying organisms first as minute 

 motile rods which he named Nitromonas. Further study and the use of solid media 

 showed that nitrification takes place in two stages and is the work of several kinds of 

 organisms. Winogradsky distinguished Nitrosomonas europaea and N. javaneyisis, 

 monotrichous rods from different regions as indicated, oxidizing ammonia to nitrites; 

 Nitrosococcus, non-motile spheres from South Amerca, effecting the same oxidation 

 as Nitrosomonas; and Nitrobacter, non-motile rods oxidizing nitrites to nitrates. 

 Subsequent authors have validated Winogradsky's names by creating the combina- 

 tions Nitrosococcus nitrosus and Nitrobacter VVinogradskyi. Subsequently, Winograd- 

 sky discovered yet other bacteria capable of the same oxidations. 



The presence of nitrifying bacteria is necessary for the normal growth of most 

 crops. So active are the nitrifying bacteria that no more than traces of ammonia and 

 nitrites are found in normal soils, and so avidly do plants absorb nitrates that these 

 accumulate only in fallow fields. 



Order 2. Actinomycetalea [Actinomycetales] Buchanan in Jour. Bact. 2: 162 



(1917). 



Organisms which consist typically of slender filaments not divided into cells, 

 but which are capable of producing conidia, that is, minute spherical or elongate 

 bodies cut off by constriction from the ends of the filaments, or of breaking up into 

 cells of the form of regular or irregular rods. Non-motile; Gram positive or Gram 

 negative; often of the staining character called acid fast. 



The order may be treated as a single family. 



