6 THE GROSS SCIENCE OF GERMS ALL AROUND YOU fives and fist bumps Handshakes transferred many bacteria Highfives Highfives transferred only half as many Fist bumps transferred only about 20 percent as many Maureen Shawn Kennedy editor-in-chief of the American Journal of Nursing thinks limiting handshakes in hospitals is an excellent idea Kennedy says There are just so many reasons to avoid handshakes even when people are washing their hands Just because someone is walking around in a white coat doesn’t mean they don’t have bacteria on their hands
WHAT ARE GERMS Most people think germs are gross But how many people really know what germs are What do they look like What do they do Do all germs cause disease There are many kinds of germs But all germs have one thing in common they are microscopic That is they are so tiny they can only be seen through a microscope Germs are also called microbes or microorganisms The prefix micro means small People who study microbes are called microbiologists KINDS OF GERMS Most germs fall into one of two groups They are either bacteria or viruses Bacteria are tiny single-celled organisms They are much smaller than the cells in the human body Most can be seen under a light microscope that magnifies them at least four hundred times Bacterial cells are also simpler than human cells Their genetic material DNA is not in a nucleus but instead floats free inside the cell 7 These highly magnified bacteria are Lactobacillus which occur naturally in the human body usually in the mouth and intestines CHAPTER ONE
8 THE GROSS SCIENCE OF GERMS ALL AROUND YOU WHAT BACTERIA LOOK LIKE Bacteria are grouped into five different categories based on the shape of their cells Rod-shaped bacteria are called bacilli E coli which lives in the human gut and Salmonella which causes food poisoning are bacilli Ball-shaped bacteria are called cocci They include Staphylococcus and Streptococcus which cause staph and strep infections Vibrios are comma-shaped comma-shaped The bacterium named Vibrio causes cholera Spiral-shaped bacteria are called spirilla One spirillum causes ulcers another causes diarrhea in children Finally spirochetes are corkscrew-shaped One type of spirochete causes Lyme disease Sometimes bacteria exist as single cells In other cases they occur in pairs chains or clusters Bacteria are enclosed by a cell wall But bacteria are living cells They get energy from the environment They duplicate their DNA and reproduce by dividing in half to form two new cells Bacteria are found everywhere They live in and on organisms including people They are found on surfaces such as tables doorknobs and clothes They live in air water and soil Most bacteria are harmless and many perform important functions in the world Only a few types of bacteria are pathogens or microbes that cause disease or infection For example bacteria cause ear infections strep throat and pneumonia Viruses are even smaller than bacteria They can only be seen by a special microscope called an electron microscope It magnifies many times more than a light microscope Viruses are not true cells They are halfway between living and nonliving They consist of pieces of genetic
WHAT ARE GERMS 9 WHAT VIRUSES LOOK LIKE Like bacteria viruses come in many shapes The icosahedron is a rounded structure composed of twenty equilateral triangles fitted together The rhinovirus which causes the common cold has an icosahedral shape An icosahedral virus enclosed in a fatty layer is called an envelope virus Influenza or flu viruses are this type Helical viruses have a capsid shaped like a cylinder Their genetic material is in the central cavity Capsid protiens proteins are arranged in a circle forming the helix The tobacco mosaic virus is helical Finally complex viruses have an icosahedral head and a helical tail They are called bacteriophages because they infect bacteria Spider like legs at the tail end attach to the bacterial cell material either DNA or RNA surrounded by a protective protein coat called a capsid Unlike bacteria viruses cannot take energy from the environment They depend on a living cell or organism for both energy and reproduction The cell or organism where they live and reproduce is the host As with bacteria viruses are everywhere They infect plants animals and bacteria They are found on surfaces and everyday objects Different viruses survive for different lengths of time outside living cells Some die in seconds others can live many years All viruses are pathogens Because they can only reproduce inside living cells they must infect something to survive This does not mean all viruses are dangerous or that all infect people A virus that infects a frog for example would
