Bacterial stress responses boost the survival of bacterium in extreme environmental conditions. Through a complex network, bacteria sense adverse conditions and respond to them via transcriptional alterations, allowing them to adapt and survive. Numerous strategies exist in bacteria to cope with stressful conditions including the formation of cysts and spores, changes in cellular membranes, expression of repair enzymes for damage, synthesis of molecules for relieving stresses, and so forth. Almost all prokaryotes have a cell wall, a protective structure that allows them to survive in both hypertonic and hypotonic aqueous conditions. Some soil bacteria are able to form endospores that resist heat and drought, thereby allowing the organism to survive until favorable conditions recur. Bacteria and archaea that are adapted to grow under extreme conditions are called extremophiles, meaning “lovers of extremes.” Extremophiles have been found in all kinds of environments: the depths of the oceans, hot springs, the Arctic and the Antarctic, in very dry places, deep inside Earth, in harsh chemical. Microorganisms do not only thrive under such a broad spectrum of parameters on Earth, but can also survive the harsh conditions of space, an environment with extreme radiation, vacuum pressure, extremely variable temperature, and microgravity. Microorganisms are ubiquitous in all kinds of micro- and macro-ecology environments on earth. They can survive even in inhospitable environments, where conditions cannot support more complex organisms, mammals and men. Microorganisms can survive in extreme climates. They are resistant to harsh climates due to their indestructible cell wall. As Pyrococcus furiosus is a microbe that is found in extreme hot climatic conditions and is isolated from shallow submarine hot springs. Archaebacteria are able to survive in harsh habitats. The presence of peptidoglycan in cell wall helps archaebacteria to survive in extreme conditions.

Pathogenic bacteria are able to sense and respond to diverse microenvironmental stresses encountered during infection. These responses allow pathogens not only to withstand specific stressful conditions but also to express virulence-associated genes in a spatio-temporally appropriate manner. Bacteria respond to stress such as nutrient deficiency or heat with an adaptation of their metabolism, known as the stringent response. "Second messengers or alarm hormones play a central role in this process," Bange explains. Alarm hormones, for example, act on processes involving the signal recognition particle SRP. Almost all prokaryotes have a cell wall, a protective structure that allows them to survive in both hypertonic and hypotonic aqueous conditions. Some soil bacteria are able to form endospores that resist heat and drought, thereby allowing the organism to survive until favorable conditions recur. Almost all prokaryotes have a cell wall, a protective structure that allows them to survive in both hypertonic and hypotonic aqueous conditions. Some soil bacteria are able to form endospores that resist heat and drought, thereby allowing the organism to survive until favorable conditions recur. Extremophiles" are organisms with the ability to thrive in extreme environments such as hydrothermal vents. Since they live in “extreme environments” they can tell us under which range of conditions life is possible. Microbes live in every kind of habitat (terrestrial, aquatic, atmospheric, or living host) and their presence invariably affects the environment in which they grow. Their diversity enables them to thrive in extremely cold or extremely hot environments. Microbes live in all types of environment, ranging from ice cold climate to hot springs; and deserts to marshy lands. They are also found inside the bodies of animals including humans. Some microorganisms grow on other organisms while others exist freely. Some bacteria produce a special type of spore called an endospore, which can withstand such extremes as boiling and freezing temperatures, and ultraviolet radiation. These bacterial endospores often endure many years of hardship before they find the growth conditions necessary for germination.