Bacteria & Viruses Chapter 19

Bacteria are Prokaryotes Unicellular Lack a nucleus & membrane bound organelles Smaller than eukaryotic cells (1-5µm)

Classifying Prokaryotes All bacteria were once placed in Kingdom Monera Now divided into 2 separate Kingdoms 1)archaebacteria 2)eubacteria

Archaebacteria Origin 3.5 billion years ago Characteristics Unusual lipids in their cell membrane Introns in their DNA Unique rRNA No peptidoglycan in their cell wall Unaffected by many antibiotics Believed to be ancestors of eukaryotes Most live in “harsh” environments

Categories of Archaebacteria Methanogens Use hydrogen gas for energy Reduce carbon dioxide to methane They live in swamps, mud, sewage, and animal guts. Extremophiles Thermophiles (60-80oC) Halophiles – salinity of 15-30% Acidophiles pH tolerant 0.7-11 Non-extremophiles Same environment as eubacteria

Kingdom Eubacteria – smallest and most abundant living organism Larger of the 2 Kingdoms “Ubiquitous” (live almost everywhere) Cell wall contains peptidoglycans Lack introns in DNA

Identifying Prokaryotes Identified by characteristics such as: Shape Chemical nature of cell wall Type of movement How they obtain energy (metabolism)

Bacterial shapes Basic Shapes Groupings Bacilli Cocci Spirilla Straight rod Cocci spherical Spirilla Long and spiral Groupings Staph- grape cluster Strep - chain

Cell walls 2 different types of cell walls are found in bacteria Gram staining is used to tell them apart Gram Positive Bacteria Gram Negative Bacteria

Movement Some do not move Flagella Spiral snake-like Glide on layer of slime

Metabolic Diversity Bacteria are more diverse in terms of metabolism than any other kingdom 2 main groups: 1)heterotrophs (most) 2)autotrophs

Heterotrophs Chemoheterotrophs: Must take in organic molecules for energy and supply of carbon. Photoheterotrophs: photosynthetic but must take in organic molecules for carbon.

Autotrophs Photoautotrophs: use light energy to convert CO2 and H2O into organic compounds. Cyanobacteria Chemoautotrophs: use energy from chemical reactions to produce organic compounds from CO2. Bacteria near deep ocean vents.

Releasing Energy & O2 Bacteria either perform cellular respiration or fermentation to release energy from food. Obligate aerobes: require oxygen Obligate anaerobes: must live in absence of oxygen Facultative anaerobes: can survive with or without oxygen

Growth and Reproduction Bacteria can grow and divide quickly. 20 minutes Bacteria only reproduce asexually by binary fission. Produces clones

Conjugation Exchange of genetic information between bacteria. Increases genetic diversity

Spore Formation When conditions become unfavorable, many bacteria form a resistant, dormant structure called an endospore

Importance of bacteria Decomposers: break down dead organisms and waste and recycle nutrients in ecosystems. Nitrogen fixers: turn nitrogen gas into a form useable by plants in a process known as nitrogen fixation. Used in industry to produce foods and beverages. Make vitamins Biotechnology uses