The figure shows scanning electron micrographs of common bacterial pathogens in humans. Part (a) is a scanning electron micrograph of Streptococcus pneumoniae which appear as chains of red oval shaped cells on a grey background. Part (b) is a scanning electron micrograph of Escherichia coli bacteria which appear as yellow rod shaped cell clustered on a grey background. Part (c) is a scanning electron micrograph of methicillin-resistant Staphylococcus aureus which appear as a chain of yellow spheres on a dark background. Part (d) is a scanning electron micrograph of Mycobacterium tuberculosis which appear as a large clump of red rod shaped bacteria on a dark background. Part (e) is a scanning electron micrograph of two Klebsiella pneumoniae bacteria which appear as two red, rod shaped cells wrapped in a long blue filament. Part (f) is a scanning electron micrograph of Neisseria gonorrhoeae which appear as individual purple kidney shaped cells on a dark background.