gange’s water purity is maintained by\tbdellovibrios\tclostridium\tferrobacillus\ttolypothrix

The correct option is 1.
Bdellovibrio is a genus of Gram-negative, obligate aerobic bacteria. One of the more notable characteristics of this genus is that members parasitize other Gram-negative bacteria by entering into their periplasmic space and feeding on the biopolymers, e.g. proteins and nucleic acids, of their hosts. After entering the periplasmic space of its host the Bdellovibrio bacterium forms a structure called a bdelloplast, which modifies both predator's and prey's cells. The predator cell can remain dormant at this stage, without affecting the viability of the host. In most cases, though, Bdellovibrio devours its prey and moves on. Because of this, Bdellovibrio can be considered bacterial predators, in addition to parasites. Bdellovibrio bacteriovorus was first described by Stolp and Starr in 1963.

Bdellovibrio bacterio vorus the reason of Ganges water cleaned It is also one of the pollution control method which could be applied anywhere since good water is the key of good health