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Typically a few micrometres in length, bacteria have a number of shapes, ranging from spheres to rods and spirals. Bacteria were among the first life forms to appear on Earth, and are present in most of its habitats. Bacteria inhabit soil, water, acidic hot springs, radioactive waste, [61] and the deep portions of Earth's crust.
The upper limit of the aerosol particle size range is determined by rapid sedimentation, i.e., larger particles are too heavy to remain airborne for extended periods of time. [ 144 ] [ 145 ] [ 129 ] Bioaerosols include living and dead organisms as well as their fragments and excrements emitted from the biosphere into the atmosphere.
Typically a few micrometres in length, bacteria have a number of shapes, ranging from spheres to rods and spirals. Bacteria were among the first life forms to appear on Earth, and are present in most of its habitats. Bacteria inhabit soil, water, acidic hot springs, radioactive waste, [63] and the deep portions of Earth's crust.
Bacteria are ubiquitous, living in every possible habitat on the planet including soil, underwater, deep in Earth's crust and even such extreme environments as acidic hot springs and radioactive waste. [25] [26] There are thought to be approximately 2×10 30 bacteria on Earth, [27] forming a biomass that is only exceeded by plants. [28]
Due to the higher density of sea water (1,030 kg m −3) than air (1.2 kg m −3), the force exerted by the same velocity on an organism is 827 times stronger in the ocean. When waves crash on the shore, the force exerted on littoral organisms can be equivalent to several tons.
[5] [2] Ultramicrobacteria possess a relatively high surface-area-to-volume ratio due to their small size, which aids in growth under oligotrophic (i.e. nutrient-poor) conditions. [2] The relatively small size of ultramicrobacteria also enables parasitism of larger organisms; [ 2 ] some ultramicrobacteria have been observed to be obligate or ...
Organic matter produced by autotrophic bacteria is then used to support the upper trophic levels. The hydrothermal vent fluid and the surrounding ocean water is rich in elements such as iron, manganese and various species of sulfur including sulfide, sulfite, sulfate, elemental sulfur from which they can derive energy or nutrients. [9]
Winds drive ocean currents in the upper 100 meters of the ocean's surface. However, ocean currents also flow thousands of meters below the surface. These deep-ocean currents are driven by differences in the water's density, which is controlled by temperature (thermo) and salinity (haline). This process is known as thermohaline circulation.