Bacteria

Bacteria (ⁱ/bækˈtɪəriə/; singular: bacterium) constitute a large domain of prokaryotic microorganisms. 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, and the deep portions of Earth's crust. Bacteria also live in symbiotic and parasitic relationships with plants and animals. They are also known to have flourished in manned spacecraft.

There are typically 40 million bacterial cells in a gram of soil and a million bacterial cells in a millilitre of fresh water. There are approximately 5×10³⁰ bacteria on Earth, forming a biomass which exceeds that of all plants and animals. Bacteria are vital in recycling nutrients, with many of the stages in nutrient cycles dependent on these organisms, such as the fixation of nitrogen from the atmosphere and putrefaction. In the biological communities surrounding hydrothermal vents and cold seeps, bacteria provide the nutrients needed to sustain life by converting dissolved compounds, such as hydrogen sulphide and methane, to energy. On 17 March 2013, researchers reported data that suggested bacterial life forms thrive in the Mariana Trench, which with a depth of up to 11 kilometres is the deepest part of the Earth's oceans. Other researchers reported related studies that microbes thrive inside rocks up to 580 metres below the sea floor under 2.6 kilometres of ocean off the coast of the northwestern United States. According to one of the researchers, "You can find microbes everywhere — they're extremely adaptable to conditions, and survive wherever they are."

Bacteria (disambiguation)

The bacteria are a major group of prokaryotic living organisms.

Bacteria may also refer to:

Fork bomb

In computing, a fork bomb (also called rabbit virus or wabbit) is a denial-of-service attack wherein a process continually replicates itself to deplete available system resources, causing resource starvation and slowing or crashing the system.

History

Around 1978 an early variant of a fork bomb called wabbit was reported to run on a System/360. It may have descended from a similar attack called RABBITS reported from 1969 on a Burroughs 5500 at the University of Washington.

Implementation

Fork bombs operate both by consuming CPU time in the process of forking, and by saturating the operating system's process table. A basic implementation of a fork bomb is an infinite loop that repeatedly launches the same process.

In Unix-like operating systems, fork bombs are generally written to use the fork system call. As forked processes are also copies of the first program, once they resume execution from the next address at the frame pointer, they also seek to create a copy of themselves; this has the effect of causing an exponential growth in processes. As modern Unix systems generally use copy-on-write when forking new processes, a fork bomb generally will not saturate such a system's memory.