n the 1700s a Dutch draper made a startling discovery Anthony van Leeuwenhoek had a passion for grind ing glass into very precise magnifying lenses He used these lenses to look close up at such things as the scrapings from his teeth He wrote I then most always saw with great wonder that in the said matter there were many very little living animalcules tiny ani mals very prettily a moving Leeuwenhoek became the first person to see and describe bacteria Since that time scientists have identified and classified thou sands of minuscule living creatures Three important categories of microorganisms bacteria algae and protozoa will be explored in this book Bacteria are prokaryotes Prokaryotes don t have a real nucleus the brain of a cell the way a eukaryotic cell such as that of an animal has Bacteria are much more primi tive in design But their simplicity also allows them to survive in many different environ ments For instance some bacteria need Oxygen some would be killed by it Others called facultative anaerobes can live with or without it Salmonella one facultative anaer obe can cause food
INTRODUCTION Some bacteria are vitally important to life Saprophytic bacteria for instance help organic matter rot and turn into rich fertile soil for growing new crops Other bacteria turn milk into cheese and yogurt And yet bacteria can also cause danger ous diseases Some bacteria even create toxins that poison their victims such as Clostridium tetani which produces tetanus Scientists have used bacteria to create bac terial antibodies to develop vaccines both to fight disease causing bacteria and the toxins they produce Algae are eukaryotes complex cells that contain chlorophyll This lets them make their own food through photosynthesis but they are simpler than plants Unlike bacte ria all of which are single celled algae can range in size Many such as dinoflagellates are single celled Others are gigantic such as the Nereocystis luetkeana kelp which can grow to be 115 feet 35 meters tall The word algae comes from a Greek word meaning seaweed and indeed seaweed is an important cate gory of algae But algae can also be found in freshwater on rocks and even on animals Many algae are beneficial for example car rageenan made from red algae is often used
A CLOSER LOOK AT BACTERIA ALGAE AND PROTOzou Women and children harvest and dry spirulina a blue green algae used as a dietary supplement in Brandji Chad in 2009 AFP Getty Images to thicken ice cream Pfiesteria on the other hand can cause an algae bloom that can kill large amounts of fish The word protozoa comes from the Greek words meaning first animal To get food some of these eukaryotes can absorb
INTRODUCTION nutrients through their pellicle or cell cover ing Others devour their prey by surrounding them and entering them into special holes called vacuoles In order to find food many protozoa have special structures that allow them to move Most commonly they use cilia short hairlike extensions that work together in waves or a flagellum a long whiplike tail to get around Others like the amoeba move by the use of pseudopods false feet They simply let some of their watery fluid pour into one area of their body until it forms a long false leg that it can use to propel itself forward While many protozoa are harm less some are parasites such as the genus Plasmodium which causes malaria a disease that kills two million people each year Leeuwenhoek and the many scientists who have discovered other bacteria algae and protozoa have done much to unlock one of the most mysterious domains of the world Scientists today continue to make discoveries by trying to live up to the great lensmaker's motto By diligent labor one discovers mat ters that could not be discerned
