In this greencast video lecture, we will try to understand about the hemoletotrophic organisms. In a simpler sense, it refers to a lifestyle of the organism dependent on inorganic chemical sussan energy source. Hemoletotrophic may be the first form of energy conservation to be evolved there in the earth system and it is widespread among the various lineages of the bacteria and archaea present in the earth. From the time of formation, the early ocean and all the earth was anoxic, that is around 4.5 billion years ago. The life has started originating only after 3.5 billion years after. The oxygen did not appear in any significant quantities there on the earth surface. Until the oxygenic photos of this is that have been carried out by the cyanobacteria as become a major even there in the course of evolution. Thus, the energy generating metabolism of the primitive said would be exclusively of anaerobic and it would have operated under a heat stable condition only since the temperature was very high in the earth surface. Remember, this hemoletotrophic organisms are need to use carbon dioxide as a sole source of carbon. So, automatically under the high temperature condition, they should also have a physiological lifestyle to fix atmospheric carbon dioxide into silk carbon. Such kind of a hemoletototrophic mechanism have been reported there with the bacteria that have been evolutionary world there in the phylogenetic tree of life. It includes bacteria like acupyx, archaeolobus that are basically autotrophic at the same time they are all hyper thermophilic in nature also. It was widely thought that, evolutionally, this old group of organisms that employs the hemoletotrophic lifestyle may be using hydrogen as a major fuel of energy for their metabolism. Virtually all the earliest evolved organisms under the category of bacteria and archaea were able to use hydrogen as an electron donor in their metabolism. Even the aebiotic reaction between the iron sulfide minerals and hydrogen sulfide have been proposed as a mechanism by which hydrogen can be able to evolve there in the system. Apart from that, ferrous ions that is Fe2 can also be able to reduce protons into hydrogen in the presence of ultraviolet radiation as an energy source. So, these processes can be able to bring out a lot of hydrogen there on their system by which hydrogen may be serving as an electron donor as well as energy for the earlier known hemoletotrophic organism. This is the earliest known hemoletotrophic process and anaerobic hemoletotrophic, that is a hemosynthesis process in which the elemental sulfur acts as an electron acceptor leading to formation of hydrogen sulfide. Simultaneously during this process carbon dioxide is getting reduced there into cell carbon by a Kelvin cycle or by any other kind of carbon fixation cycle that may be operated there in the earlier environment. Thus the earliest hemoletotrophic organism that have been proliferated there in the air surface includes mainly of methanogens which can be able to reduce carbon dioxide with the help of hydrogen as an energy source. The next important group is the sulfate reducing bacteria which again use hydrogen as a redactant for their growth process. The process of hemoletotrophic was first described by Veno-Gratzky. He has referred that one as an anorgoxidension that is literally meaning inorganic oxidizes group of organisms. So he refers hemoletotrophic as an energy metabolism of bacteria that uses the oxidation of inorganic substances in the absence of light as a source of energy for cell biosynthesis and maintenance. Another term that has been related that with the hemoletotrophic is hemosynthesis. It was coined in 1897 by Fiffer. It refers to metabolism of bacteria that uses inorganic compounds oxidation to support the autotrophic carbon dioxide fixation or carbon assimilation. The important group of hemoletotrophic backlyus which we are going to study in this paper includes the nitrifices, sulfur oxidizes, ion oxidizes, hydrogen bacteria, carboxid bacteria as well as the methane oxidizer and producers. In the second column you can able to see which molecule serving as an energy and the third column shows the products that have been produced when that particular energy source have been used.