4. Key features No nucleus DNA in simple ring structure free in cytoplasm Cell wall present, not made of cellulose but peptidoglycans ( polymer of sugar and amino acids) Cell membrane controlling passage of substances into and out of the cell Lack of membrane bound organelles Infolding of the cell membrane called mesosome is the site of respiration Ribosomes (18nm diameter) free in cytoplasm are the sites of protein synthesis Cell size – 0.5 and 5 µm Cells divide by binary fission with no spindle formation
5. Gram positive and gram negative bacteria One of the major differences between types of bacteria is the ability to stain their cell walls using a procedure called Gram staining. Bacteria which have cells walls which take up the stain = Gram positive Those that do not = gram negative Useful as both types of bacteria respond differently to antibiotics.
6. Gram Negative bacteria E.g. E-Coil Thinner layer of peptidoglycan and no teichoic acid between two layers of membrane, then outer layer of lipopolysaccharides Stain does not stick
7. Viruses Smallest microorganism 0.02-0.3µm across 50x smaller than average bacterium Not cells Arrangement of protein and genetic material Invade other cells take over biochemistry to make more copies.
10. Features of viruses Have a protein coat (capsid) around a core containing nucleic acid and virus enzymes Lack of internal membranes, cytoplasm and ribosomes Some have an outer envelope taken from the host’s cell surface membrane – it contains lipids and proteins Viral envelopes have glycoproteins which are recognised by the host immune system – helps virus attach to cell and penetrate the membrane
![Bacteria and Viruses ,[object Object]](https://image.slidesharecdn.com/bacteriaandviruses-111006094204-phpapp01/85/Bacteria-and-viruses-1-320.jpg)
![Describe the role of microorganisms in the decomposition of organic matter and recycling of carbon,[object Object]](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)