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Graphic depicting the human skin microbiota, with relative prevalences of various classes of bacteria. The human microbiome is the aggregate of all microbiota that reside on or within human tissues and biofluids along with the corresponding anatomical sites in which they reside, [1] [2] including the gastrointestinal tract, skin, mammary glands, seminal fluid, uterus, ovarian follicles, lung ...
In bacteria, both nutrients and waste products of metabolism reach the interior of the cell by diffusion, which places an upper limit on the size of these organisms. Cells of the large sulfur bacterium Thiomargarita namibiensis, discovered in 1999, contain a large sac filled with water and nitrates, which pushes most of the cytoplasm close to ...
The temperature and pH of saliva makes it conducive for bacteria to survive in the oral cavity. Bacteria in the oral cavity include Streptococcus mutans, Porphyromonas gingivalis, and Staphylococcus. [15] S. mutans is the main component of the oral microbiota. [15] A healthy oral microbiome decreases oral infections and promotes a healthy gut ...
The measurement of an exponential bacterial growth curve in batch culture was traditionally a part of the training of all microbiologists; the basic means requires bacterial enumeration (cell counting) by direct and individual (microscopic, flow cytometry [1]), direct and bulk (biomass), indirect and individual (colony counting), or indirect ...
Bacteria function and reproduce as individual cells, but they can often aggregate in multicellular colonies. [54] Some species such as myxobacteria can aggregate into complex swarming structures, operating as multicellular groups as part of their life cycle , [ 55 ] or form clusters in bacterial colonies such as E.coli .
As the cell size increases, they make proportionately less ATP, thus energy production limits their size. [3] Thiomargarita are an exception to this size constraint, as their cytoplasm forms along the periphery of the cell, while the nitrate-storing vacuoles occupy the center of the cell. [28] These vacuoles make up most of the cell.
As resources become more limited, the growth rate tapers off, and eventually, once growth rates are at the carrying capacity of the environment, the population size will taper off. [6] This S-shaped curve observed in logistic growth is a more accurate model than exponential growth for observing real-life population growth of organisms.
Pathogenic bacteria are bacteria that can cause disease. [1] This article focuses on the bacteria that are pathogenic to humans. Most species of bacteria are harmless and many are beneficial but others can cause infectious diseases. The number of these pathogenic species in humans is estimated to be fewer than a hundred. [2]