Taibah University Medical Microbiology Lecture 1 PDF

Taibah University Faculty of applied medical sciences AlUla Medical Microbiology The Science of Microbiology Dr. Saloua Sahbani Lecture 1 1 Outline  I. Prokaryotes  II. Intracellular...

Taibah University Faculty of applied medical sciences AlUla Medical Microbiology The Science of Microbiology Dr. Saloua Sahbani Lecture 1 1 Outline  I. Prokaryotes  II. Intracellular structure 2 What Is Microbiology and Why Does It Matter?  Microbiology is the study of microorganisms, a large and diverse group of microscopic organisms that exist as single cells or cell clusters.  it also includes viruses, which are microscopic but not cellular. 3 Bacteria They are responsible for 1- Cycling the chemical elements essential for life including: carbon, nitrogen, sulfur, hydrogen, and oxygen. 2- More photosynthesis is carried out by microorganisms than by green plants. 3- Furthermore, there are 100 million times as many bacteria in the oceans (13 × 1028 ) as there are stars in the known universe. 4 Bacteria cont.  Humans have an intimate relationship with microorganisms; more than 90% of the cells in our bodies are microbes.  The bacteria present in the average human gut weigh about 1 kg, and a human adult will excrete his or her own weight in fecal bacteria each year.  The number of genes contained within this gut flora outnumber that contained within our genome 150-fold, and even in our own genome, 8% of the DNA is derived from remnants of viral genomes. 5 I- Prokaryotes The primary distinguishing characteristics of the prokaryotes are their relatively small size, usually on the order of 1 μm in diameter, and the absence of a nuclear membrane. The DNA of almost all bacteria is a circle with a length of about 1 mm; this is the prokaryotic chromosome. Most prokaryotes have only a single chromosome. 6  I.1. Prokaryotic Diversity Some prokaryotes such as the purple bacteria convert light energy to metabolic energy in the absence of oxygen production. Other prokaryotes, exemplified by the blue-green bacteria (Cyanobacteria), produce oxygen that can provide energy through respiration in the absence of light. Aerobic organisms depend on respiration with oxygen for their energy. 7  I.2. Prokaryotic Communities If the organisms within a physically interconnected community are directly derived from a single cell, the community is a clone that may contain up to 108 cells. Bacteria and Archaebacteria: The Major Subdivisions Within the Prokaryotes Major success in molecular phylogeny has been the demonstration that prokaryotes fall into two major groups 1- Bacteria 2- Archaebacteria, has received relatively little attention until recently, partly because many of its representatives are difficult to study in the 8 laboratory. I.2. Prokaryotic Communities cont. 9 I.3. Structures of the bacterial Cell 10 I.4. Structures of the bacterial Cell cont. They were first seen under a microscope by Anton Van Leeuwenhoek in 1676 As microscopes have improved, scientists have come to understand bacterial cell structure better 11 1.4. Structures of the bacterial Cell cont. 12 1.4. Structures of the bacterial Cell cont. 13 1.4. Structures of the bacterial Cell cont. 14 II. Intracellular structure 15 II.1. Cytoplasm 16 II.2. Constituents of cytoplasm 17 II.3. Nucleoid 18 II.4. Plasmid 19 II.4. Plasmid cont. 20 II. 5. Plasmid function 21 II.6. Ribosomes-protein synthesis machinery 22 II.7. Bacterial chromosome 23