Question

Bacteria found in hot acidic aerobic conditions are
(a) Halophiles
(b) Thermoacidophiles
(c) Methanogens
(d) Rickisittae

Answer 1

Hint: The bacteria found in hot acidic aerobic conditions can generate energy for the synthesis of food by oxidizing sulphur to sulphuric acid. Modification in their cell membrane has helped them to survive and thrive in extreme habitats.

Complete answer:
Thermoacidophiles like Thermoplamsa and Thermoproteus are the archaebacteria which have the twofold ability to tolerate a high temperature as well and an acidic environment. They are habitually found in acidic sulphur springs where the temperature may exceed 80°C and pH be as low as 2. They are chemosynthetic as they obtain energy by synthesizing food from oxidizing sulphur to sulphuric acid. They can survive such harsh conditions mainly due to two main reasons:
ㅡ Branched-chain lipids are present in the cell membrane of Thermoacidophiles.
 ㅡThey possess special resistant enzymes which remain functional even in high temperatures and do not denature.

Additional Information: Archaebacteria are of three major types - methanogens, halophiles and thermoacidophiles.
Methanogens are obligate anaerobes i.e. they are strictly anaerobes. They are gram-negative bacteria and chemoautotrophs as they use hydrogen as a source of electrons for reducing carbon dioxide to food and give off methane as a byproduct. They are found in swamps, marshy areas, sewage and also in the rumen of cattle and our colon. E.g. Methanobacterium, Methanococcus.
Halophiles are named so because they are normally found in salt-rich areas such as the Dead sea, salt marshes. They are capable of surviving these high salt conditions due to the presence of special lipids in the cell membrane, absence of sap vacuoles hence plasmolysis, presence of mucilage covering and high internal salt concentration. E.g. Halobacterium, Halococcus.
Rickettsiae represents a class of obligate intracellular bacteria that are pathogenic. They are transmitted by bites of tick and fleas.
So, the correct answer is ‘Thermoacidophiles.’

Note: Archaebacteria are a group of most primitive prokaryotes depicting one of the earliest life forms of earth. They are particularly known for the absence of peptidoglycan in their wall which is an important component in those of eubacteria. Instead, the cell wall contains branched lipid side chains which decrease membrane fluidity and increase tolerance to extreme heat as well as low pH.