 Psychrophiles, cells that grow best at low temperatures below 20oC  Mesophiles have temperature optima in the range of 20 to 50oC  Thermophiles grow best at temperatures greater than 50oC.

 Aerobic microorganisms require O2 for growth and metabolism.  Anaerobic microorganisms are inhibited by the presence of O2  Facultative organisms can switch the metabolic pathways

 Can grow with only little moisture  A few dissolved minerals  These bacteria are photosynthetic and can convert CO2 from the atmosphere into the organic compounds  They can convert N2 to NH3

 Organisms from extreme environments are called extremophiles  They provide the human race with important tools for processes to make useful chemicals and medicinals.  Can be used in the recovery of metals from low-grade ores or in the desulfurization of coal or other fuels

 Spherical (Coccus- cocci)  Cylindrical (rod or bacillus-bacilli)  Ellipsoidal (Coccus- cocci)  Spiral (spirillum-spirilla)  Pleomorphic cells

 Procaryotes  have a simple structure with a single chromosome  No nuclear membrane, no organelles, such as mitochondria, endoplasmic reticulum.

 Eucaryotic cells  have more than one chromosome (DNA molecule) in the nucleus.  have a true nuclear membrane  contain mitochondria  Endoplasmic reticulum  Golgi apparatus  a variety of specialized organelles

 EucaryotesEucaryotic Plants, Animals, Protists (Algae, fungi, protozoa) EubacteriaProcaryotic Most bacteria Archaebacteria Procaryotic Methanogens, halophiles, thermoacidophiles

 Gram-negative cell (E. coli) has an outer membrane supported by a thin peptidoglycan layer.  Gram-positive cells (Bacillus subtilis) do not have an outer membrane, have a very thick, rigid cell wall with multiple layers of peptidoglycan Mycoplasma (not gram positive or gram negative

 Actinomycetes are bacteria, but, morphologically, resemble molds.  Cyanobacteria(blue-green algae) have chlorophyll and fix CO2 into sugars.  Anoxygenic photosynthetic bacteria(purple and green bacteria) have light-gathering pigments called bacteriochlorophyll.

 Ribosomes are the site of protein synthesis, consists of 63% RNA and 37% protein.  Storage granules are used as a source of key metabolites and contain polysaccharides, lipids, sulfur granules.  Bacterial spores are produced as a resistance of adverse conditions such as high temperature, radiation, toxic chemicals.  Volutin is granular intracellular structure, made of inorganic polymetaphosphates.

 Archaebacteria have no peptidoglycan  The nucleotide sequences in the ribosomal RNA are similar within the archaebacteria but different from eubacteria  The lipid composition of the cytoplasmic membrane is very different for the two groups.

 The nucleus of eucaryotic cells contains chromosomes as nuclear material (DNA molecules with associated small proteins), surrounded by a membrane.  The nucleolus is the site of ribosome synthesis.  Many chromosomes contain small amounts of RNA and basic proteins called histones attached to the DNA.  Each chromosome contains a single linear DNA molecule on which the histones are attached.

 Mitochondria are the powerhouses of a eucaryotic cell, where respiration and oxidative phosphorylation take place.  The mitochondria contain a complex system of inner membranes called cristae.  A mitochondria has its own DNA and protein-synthesizing machinery and reproduces independently.

 The endoplasmic reticulum is a complex, convoluted membrane system leading from the cell membrane into the cell.  The rough endoplasmic reticulum contains ribosomes and is the site of protein synthesis and modifications of protein structure after synthesis.  The smooth endoplasmic reticulum is involved with lipid synthesis.

 Lysosomes are very small membrane- bound particles that contain and release digestive enzymes.  Peroxisomes carry out oxidative reactions that produce hydrogen peroxide.  Glyoxysomes are very small membrane- bound particles that contain the enzymes of the glyoxylate cycle.

 Golgi bodies are very small particles composed of membrane aggregates and are responsible for the secretion of certain proteins.  Vacuoles are membrane-bound organelles of low density and are responsible for food digestion, osmotic regulation, and waste- product storage.  Chloroplasts are relatively large, chlorophyll- containing, green organelles that are responsible for photosynthesis in photosynthetic eucaryotes, such as algae and plant cells.

 Pseudomonas sp. (bacterium)  Geotrichum candidum (yeast)  Mucor miehei (fungus)  Rhizopus delemar (fungus)

Michael L. Shuler and Fikret Kargı, Bioprocess Engineering: Basic Concepts (2 nd Edition),Prentice Hall, New York, James E. Bailey and David F. Ollis, Biochemical Engineering Fundementals (2 nd Edition), McGraw- Hill, New York, 1986.