text: The survival of these bacteria is dependent on the physiochemical conditions of their environment. Although they are sensitive to certain factors such as quality of inorganic substrate, they are able to thrive under some of the most inhospitable conditions in the world, such as temperatures above 110 degrees Celsius and below 2 pH.  The most important requirement for chemolithotropic life is an abundant source of inorganic compounds, which provide a suitable electron donor in order to fix CO and produce the energy the microorganism needs to survive. Since chemosynthesis can take place in the absence of sunlight, these organisms are found mostly around hydrothermal vents and other locations rich in inorganic substrate.
  The energy obtained from inorganic oxidation varies depending on the substrate and the reaction.  For example, the oxidation of hydrogen sulfide to elemental sulfur by ½O produces far less energy (50 kcal/mol or 210 kJ/mol) than the oxidation of elemental sulfur to sulfate (150 kcal/mol or 627 kJ/mol) by 3/2 O,. The majority of lithotrophs fix carbon dioxide through the Calvin cycle, an energetically expensive process.  For some low-energy substrates, such as ferrous iron, the cells must cull through large amounts of inorganic substrate to secure just a small amount of energy.  This makes their metabolic process inefficient in many places and hinders them from thriving.