SP. N.l

• Main Authors: Stanley W. Watson, Woods Hole
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: South Atlantic Ocean
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.525.53; http://www.aslo.org/lo/toc/vol_10/supplement2/R0274.pdf

A new species of an ammonia-oxidizing bacterium, Nit~osocystis oceanus, is described. This is the first nitrifying bacterium ever isolated from open ocean waters and the first species of the genus Nitrosoct~stk observed in over 30-years. The cells are gram negative, spherical to ellipsoidal, 1.8-2.2 p in diameter, and occur as single cells, diploids, and occasionally as tetrads. Cells at times formed cysts and zoogloea. The most consistent and outstanding generic characteristic is the ultrastructurc of the cells. Cells of this genus have a cytomem-brane organelle composed of a series of flattened vesicles that transverse and bisect the cell; while cells of Nitrosomonus sp. lack this complex membranous organelle, they do have one to two concentric membranes at the periphery of the ccl1 adjacent to the plasma membrane. Ni~rosocystti ocennzcs is an obligate autotroph using only ammonia as an energy source and carbon dioxide as a carbon source. This bacterium grows optimally at 30C and in ammonia concentrations of 5 X 10 ”- 2.4 x 10 ”,ug-at. NHa-N/liter. It is an obligate halophile, re-quiring natural seawater for growth, and it lyses when suspended in distilled water. Grow-ing optimally in continuous cultures, individual cells produced 2 X lo- ’ ELM of NOa- per day. Nitrosocystis oceunus was cultured repeatedly from offshore waters of the western North and South Atlantic Ocean since 1959. It is estimated that the standing crop of these organisms is less than one bacterium per ml. This number of bacteria in the upper 100 m of tropical waters would produce approximately 0.07 E.cg-at. NO,--N liter- ’ year-I.