Cocci→ Cocci may be oval,elongated, or flattened on oneside.→ Cocci may remain attachedafter cell division. These groupcharacteristics are often usedto help identify certain cocci.
Cocci that remain inpairs after dividingare called Diplococci.Cocci that remain inchains after dividingare calledStreptococci.Cocci that divide intwo planes andremain in groups offour are calledTetrads.Cocci that divide inthree planes andremain in groupscube like groups ofeight are calledSarcinae.Cocci that divide inmultiple planes andform grape likeclusters or sheets arecalled Staphylococci.
Bacilli→ Since bacilli only divideacross their short axis thereare fewer groupings.
Most bacilli appear assingle rods.Diplobacilli appear inpairs after division.Streptobacilli appearin chains after division.Some bacilli are soshort and fat that theylook like cocci and arereferred to as
Spiral bacteria→Spiral bacteria have one or more twists.
Vibrios look like curvedrods.Spirilla have a helicalshape and fairly rigidbodies.Spirochetes have ahelical shape andflexible bodies.Spirochetes move bymeans of axial
Other shapes Haloarcula, a genus ofStella are star-shaped. halophilic archaea, are rectangular.