Division in random planes produces a staphylococcus arrangement ( see Fig. Differences in the cell-wall structure are apparently the limiting factors for some cell shapes in a certain group of bacteria: e.g., spiral in gram-positive, filamentous in gram-negative.

It is difficult with a conventional light microscope to tell a tetrad arrangement (square of four cocci) from a sarcina arrangement (cube of eight) so in our lab, anytime you see ba square of four cocci, say it is either a tetrad or a sarcina arrangement.ĭ. Division in three planes produces a sarcina arrangement ( see Fig. Scanning electron micrograph of Micrococcus luteusĬ. Division in two planes produces a tetrad arrangement ( see Fig. Scanning Electron Micrograph of Enterococcusī. Transmission electron micrograph of Streptococcus Scanning electron micrograph of Streptococcus pyogenes courtesy of Dennis Kunkel's Microscopy Scanning electron micrograph of a Neisseria, a diplococcus courtesy of Dennis Kunkel's Microscopy Theyre so small that if you lined up a thousand of them end to end, they could fit across the end of a pencil eraser. Bacteria are one-celled organisms that can be seen only with a microscope. Categories include: Bacteria Viruses Fungi Protozoans Helminths Bacteria. Scanning electron micrograph of a Streptococcus pneumoniae, a diplococcus It may not be easy to recognize life on an alien world, so scientists look for proofs in many directions: objects with shapes and sizes that seem reasonable. Infectious agents come in many shapes and sizes.

Bacteria shapes and sizes