Aerobic Heterotrophs Research Articles

Asticcacaulis biprosthecum sp.nov. Life cycle, morphology and cultural characteristics.

Asticcacaulis biprosthecum sp. n. is a gram-negative aerobic heterotroph which undergoes a dimorphic life cycle typical of bacteria of the caulobacter group. Prosthecae of these cells are shown to be structurally homologous with prosthecae of two strains ofCaulobacter crescentus. The general physiological and cultural characteristics are recorded.

Nitrogen fixation in the rhizosphere of marine angiosperms

High rates of acetylene reduction were observed in systems containing excised rhizomes of the Caribbean marine angiosperms Thalassia testudinum, Syringodium filiforme and Diplanthera wrightii, and the temperate marine angiosperm Zostera marina. For 4 plant and plant-sediment systems the ratio of acetylene reduced/N2 fixed varied from 2.6 to 4.6. For T. testudinum the estimated rates of nitrogen fixation are in agreement with estimated requirements of the plant for nitrogen. For a typical T. testudinum stand, N2 fixation is estimated to be 100 to 500 kg N/hectare per year. Numbers of N2-fixing bacteria in the rhizosphere sediments were roughly 50 to 300 times more abundant than those in the nonrhizosphere sediments, and in both types of sediments were of the same orders as the estimated numbers of heterotrophic aerobes.

Preventing Foodborne Illness: Bacillus cereus and Bacillus anthracis

Bacillus species are Gram positive, aerobic heterotrophs, ubiquitous bacteria, characterized by their ability to form resistant spore coats. There are about 48 known species in the genus Bacillus but only B. anthracis and B. cereus are associated with human disease. Bacillus species are mesophilic bacteria that produce heat-resistant endosopores with a growth range of 10°C to 48°C, with optimal growth at 28°C to 35°C. In addition, they can grow in a broad pH range of 4.9 to 9.3. This document is FSHN04-05, one of a series of the Food Science and Human Nutrition Department discussing common foodborne pathogens of interest to food handlers, processors and retailers; Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Date published: November 2004.

Activity of microorganisms in acid mine water. I. Influence of acid water on aerobic heterotrophs of a normal stream.

Comparison of microbial content of acid-contaminated and nonacid-contaminated streams from the same geographical area indicated that nonacid streams contained relatively low numbers of acid-tolerant heterotrophic microorganisms. The acid-tolerant aerobes survived when acid entered the stream and actually increased in number to about 2 x 10(3) per ml until the pH approached 3.0. The organisms then represented the heterotrophic aerobic microflora of the streams comprised of a mixture of mine drainage and nonacid water. A stream which was entirely acid drainage did not have a similar microflora. Most gram-positive aerobic and anaerobic bacteria died out very rapidly in acidic water, and they comprised a very small percentage of the microbial population of the streams examined. Iron- and sulfur-oxidizing autotrophic bacteria were present wherever mine water entered a stream system. The sulfur-oxidizing bacteria predominated over iron oxidizers. Ecological data from the field were verified by laboratory experiments designed to simulate stream conditions.