Stanley W. Watson

Nitrospira marina gen. nov. sp. nov.: a chemolithotrophic nitrite-oxidizing bacterium

A new chemolithotrophic nitrite-oxidizing bacterium, for which the name Nitrospira marina is proposed, was isolated from the Gulf of Maine. N. marina is a Gramnegative curved rod which may form spirals with 1 to 12 turns. Cells have a unique periplasmic space and lack intracytoplasmic membranes and carboxysomes. N. marina is an obligate chemolithotroph, but best growth is obtained in a mixotrophic medium. N. marina may be one of the most prevalent nitrite-oxidizing bacteria in some oceanic environments. Type strain is field with American Type Culture Collection (ATCC 43039).

A Cyanobacterium Capable of Swimming Motility

A novel cyanobacterium capable of swimming motility was isolated in pure culture from several locations in the Atlantic Ocean. It is a small unicellular form, assignable to the genus Synechococcus, that is capable of swimming through liquids at speeds of 25 micrometers per second. Light microscopy revealed that the motile cells display many features characteristic of bacterial flagellar motility. However, electron microscopy failed to reveal flagella and shearing did not arrest motility, indicating that the cyanobacterium may be propelled by a novel mechanism.

Characteristics of two marine nitrite oxidizing bacteria, Nitrospina gracilis nov. gen. nov. sp. and Nitrococcus mobilis nov. gen. nov. sp.

SummaryTwo new nitrite oxidizing bacteria for which the names Nitrococcus mobilis and Nitrospina gracilis are proposed were isolated from the marine environment. Nitrococcus mobilis was cultured from South Pacific waters and it is a large motile coccus with unique tubular cytomembranes. Nitrospina gracilis was isolated from South Atlantic waters and it is a long slender rod which lacks an extensive cytomembrane system. Both are obligate marine organisms and both are obligate chemoautotrophs. The fine structure of these organisms is detailed.

The Family Nitrobacteraceae

The biological oxidations of ammonia to nitrite and nitrite to nitrate, collectively referred to as nitrification, are carried out in nature by two physiological groups of Gram-negative, chemolithotrophic bacteria. The organisms in both groups fix carbon dioxide via the Calvin cycle (Campbell, Hellebust, and Watson, 1966) for their major source of cell carbon and derive their energy and reducing power either from the oxidation of ammonia (ammonia-oxidizing bacteria) or nitrite (nitrite-oxidizing bacteria). With the exception of a few strains of Nitrobacter winogradskyi, which can be grown chemoheterotro-phically, the nitrifying bacteria are obligate chemo-lithotrophs.

Freeze-Etching of Bacteria

Publisher Summary The first electron micrographs of bacterial cells were published about 20 years ago. These early studies suggested the presence of definite intracellular structures. Sectioning techniques, originally developed for eucaryotic cells, were gradually modified so that thin sections of bacteria could be obtained. These first thin sections of procaryotic cells revealed an unsuspected level of intracellular complexity. While electron microscopes have advanced technically, preparative techniques for biological material have not kept pace. The newest models have a potential resolution of 0.2-0.3 nm but less refined preparative techniques have denied biologists the use of this degree of sophistication. Some difficulties encountered in the preparation of biological material for electron microscope examination are intrinsic and unavoidable. Live bacteria cannot be examined in thin section and the process of fixation and dehydration frequently alters or even extracts cellular components, leaving the degree of preservation of structural integrity open to question. About 10 years ago, a new technique permitting the replication of freeze-fractured live biological specimens was developed. This method allowed the internal morphology of cells that had neither been dried nor chemically fixed to be seen, thereby eliminating or minimizing many of the artifacts typically introduced. This chapter discusses the technique of freeze-etching; its application in bacterial cytology, morphology, and related fields; and its possible future development in microbiology.

A lobular, ammonia-oxidizing bacterium, Nitrosolobus multiformis nov.gen.nov.sp.

SummaryNitrosolobus multiformis is a lobular shaped, previously undescribed ammonia-oxidizing bacterium. The organism is ubiquitous and was isolated from soil samples obtained in various parts of the world. Its lobular nature and its internal, partially compartmentalized cytoplasm makes it morphologically unique and easily distinguishable from all other microorganisms. Physiological compartmentalization also occurs and is characterized by glycogen deposition in the peripheral compartments of the cell. The cells are obligate chemoautotrophs using CO2 and ammonia as primary carbon and energy sources. Its obligate chemoautotrophic nature stems primarily from a metabolic deficiency. Even though the cells cannot be grown on an organic medium the cells still have a slight heterotrophic potential and are able to oxidize and assimilate minute amounts of acetate in the absence of an inorganic energy source.

Cell envelope of Nitrosocystis oceanus

The cell envelope of Nitrosocystis oceanus , a marine nitrifying bacterium, has been shown to be composed of seven distinct layers including an outer fibrous slime layer, a hexagonal layer comprised of 50 A subunits, a double-tracked layer consisting of 40 A subunits, two globular layers which are separated by a mucopeptide layer, and a plasma membrane. These studies show that N. oceanus cell envelopes differ from those found in Escherichia coli and other Gramnegative bacteria and illustrate the value of combining freeze-etching with other electron microscopic techniques for the study of bacterial cell envelopes.

Macromolecular Subunits in the Walls of Marine Nitrifying Bacteria

The outteromost laver of the cell wall of all marine ammonia-oxidizing bacteria So far isolated is made up of protein subunits arranged in a regular manner and linked together through metal-oxygen bonds. This sculptured, outer wall layver appears to be uniique to the terrestrial ammonia-oxidizing bacteria.

Reisolation of Nitrosospira briensis S. Winogradsky and H. Winogradsky 1933

SummaryNitrosospira briensis was isolated from the soils of Crete, the Greek mainland and Switzerland. This is only the second report of the reisolation of a member of this genus since it was described by the Winogradskys in 1933. N. briensis, studied in the present investigation, is so tightly coiled that the cells appear as rods or cylinders rather than spirals when examined with the phase- contrast microscope. On occasion the cells partially uncoil and the spirals are clearly evident even with a phase-contrast microscope. When the cells were thin-sectioned, shadowed, negatively-stained or freeze-etched and viewed with the electron microscope, the spirals were visible even in tightly coiled cells. The tightly coiled cells which appear as rods or cylinders are 1.5–2.5 μ long and 0.8–1.0 μ wide. The cells moved erratically and are propelled by 1–6 flagella which were 3–5 μ long.

The Sterile Hot Brines of the Red Sea

The brines of the Atlantis II and Discovery Deeps, their sediments and the water overlying these Red Sea brines were examined for the presence or absence of bacteria. No bacteria were found in the Atlantis II sediments and brines, but they were present in the overlying transition and normal 22° waters. The sulfate reducing bacteria in this transition layer may account for the sulfur fractionation found in the metal sulfides in the sediments. In the Discovery Deep, bacteria were present in the sediment but were not demonstrated within the brines. The high temperature, salinity and metal concentrations in the Atlantis II brines are thought to act synergistically, preventing the growth of bacteria. The lower heavy metal concentration in Discovery Deep may make conditions slightly less hostile to life and permit the growth of bacteria in the sediments.