Ministry of Higher Education and Scientific Research Salahaddin

Ministry of Higher Education and Scientific Research Salahaddin University-Erbil College of Science Environmental Science Department Aquatic Microbiology Prokaryotic Cells

Review of the Previous Lecture: We studied the following concepts in our previous class: �Ecosystem Structure and Function �Trophic structure of an ecosystem �Different Trophic Levels 2

Microbiology �Microbiology: is the study of microorganisms, which are tiny organisms that live around us and inside our body. �An organism is a living that ingests and breaks down food for energy and nutrients. You are an organism and so are dogs, cats, insects, and other creatures that you see daily. 3

�Aquatic Microbiology: is the study of tiny organisms in water environment (systems). �Aquatic Environment: Virtually all water systems contains living organisms, which vary greatly with different aquatic environments, from fresh water to sea water. 4

Aquatic Environment is divided into the following zones: �Pelagic zone: composed of open water. �Benthic zone: near the bottom. �Sediment zone: similar to soil. 5

�The most important microorganisms live in the photic zone also called (productive zone) the region of the pelagic zone penetrated by sunlight & therefore capable of supporting photosynthesis; these aquatic microorganisms are phytoplankton, free-floating cyanobacteria & algae. 6

�Marin Microbiology: microorganisms contribute to the ecology of aquatic ecosystems in several ways in addition to decomposition & nutrient cycling. �Fresh water Microbiology: fresh water ecosystems are less stable than oceans & seas & are more susceptible in temperature, p. H, & O 2 concentration. They are also more susceptible than oceans to the immediate effects of pollution. 7

�The living organism's communities in water are divided in to the following: 1 - Prokaryotic Cells 2 - Eukaryotic Cells 8

Prokaryotic Cells �A prokaryotic cell is a cell that does not have a true nucleus. The nuclear structure is called a nucleoid, which contains most of the cell’s genetic material and is usually a single circular molecule of DNA. A prokaryotic organism, such as a Bacteria, living microorganisms, having different sizes, shapes, arrangements & structures, . eg. Salmonella sp. , Vibrio sp. 9

�Bacterium is a cell that lacks a membrane-bound nucleus or membrane-bound organelles. �Archaea, can exist in very hot and very cold environments, making them resilient microorganisms that can survive attacks and destroy other bacteria. �Which can survive and grow in an oxygen-free environment (anaerobic) and in a high-salt (hypersaline) environment. 10

Procedure �Materials: �Nutrient agar �Water sample �Petri dishes �Distilled water 11

�Pour plate method is usually the method of choice for counting the number of colony-forming bacteria present in a liquid specimen. In this method, fixed amount of inoculum (generally 1 ml) from a broth/sample is placed in the center of sterile Petri dish using a sterile pipette. Molten cooled agar (approx. 15 m. L) is then poured into the Petri dish containing the inoculum and mixed well. After the solidification of the agar, the plate is inverted and incubated at 37°C for 24 -48 hours. 12