Effective transformation can also be achieved by propelling microparticles of DNA-coated gold or tungsten at algal cells [41, 42 and 43]. One drawback to microparticle bombardment is its forceful nature — comparable to shooting a baseball through a basketball at over 1000 miles per hour. A less aggressive approach involves the microbe Agrobacterium tumefaciens, which causes tumors in plants [ 44]. Through genetic manipulation of the bacterium's T-DNA (transfer DNA), tumor-inducing genes can be replaced with useful gene constructs, which can then be introduced into microalgal cells [ 45].