Microbiology - The Bacteria | Anatomy and Physiology

Preview (5 of 14 Pages)

100%

Microbiology - The Bacteria - Page 1 preview image

Loading page ...

Study GuideMicrobiology–The Bacteria1.Gram-Negative Rods and CocciGram-negative bacteria include many different shapes and lifestyles. Some live freely in nature, somehelp plants and animals, and others can cause disease. Let’s explore the major groups step by step.1.1Bdellovibrios–Bacteria That Hunt Other BacteriaBdellovibrios areaerobic, Gram-negative, curved rod-shaped bacteriawith a very unusuallifestyle. Instead of living on nutrients in the environment, theyprey on other bacteria.The bdellovibrio attaches to another bacterium, spins, anddrills a hole through the host’s cell wall.It then enters the space between the cell wall and the plasma membrane. Once inside, it takes controlof the host’s cell machinery and grows. This process eventuallykills the host bacterium.The best-studied species in this group isBdellovibrio bacteriovorus, which has a distinctivecomma-like shape.1.2Pseudomonads–Common and Versatile BacteriaPseudomonads areaerobic, Gram-negative rodsthat move usingpolar flagella. There aremorethan 30 speciesin this group.One well-known species,Pseudomonas fluorescens, produces ayellow-green pigment. Anotherimportant species,Pseudomonas aeruginosa, is medically significant because it can causeurinarytract infectionsandinfections in burned tissue.1.3Azotobacter and Rhizobium–Nitrogen FixersSpecies ofAzotobacterandRhizobiumare extremely important because they canfix nitrogenfromthe atmosphere.•Azotobacterlives freely in the soil.•Rhizobiumlives on the roots oflegume plants.

Microbiology - The Bacteria - Page 2 preview image

Loading page ...

Study GuideThese bacteria use special enzymes to convertatmospheric nitrogeninto organic nitrogencompounds that plants can use. Plants then use these compounds to makeamino acids andproteins, which become an important food source for animals and humans.Azotobacter species can also form aresting structure called a cyst, which helps them survivedrying and harsh environmental conditions.1.4Enterobacteria–Intestinal BacteriaEnterobacteria arefacultatively anaerobic, Gram-negative rodsthat normally live in thehumanintestine. They belong to the familyEnterobacteriaceae.More than25 generaare included in this group, and many are medically important. Examplesinclude:•Salmonellaspecies, which causesalmonellosis•Yersinia pestis, the cause ofplague•Klebsiellaspecies, which causepneumonia and intestinal infections•SerratiaandProteusspecies•Escherichia coli, a well-known member of this groupAll enterobacteria haveperitrichous flagella, meaning flagella are spread over the entire surface ofthe cell.1.5Vibrios–Curved Rods of Medical ImportanceVibrios arecurved, Gram-negative, facultatively anaerobic rodsthat belong to the familyVibrionaceae.One very important species isVibrio cholerae, which causescholerain humans. Other relatedgenera, such asAeromonasandPlesiomonas, are also associated withintestinal diseases.Some marine vibrios, especiallyPhotobacteriumspecies, can produce light through a chemicalreaction involving the enzymeluciferase. This light production is calledbioluminescence.

Microbiology - The Bacteria - Page 3 preview image

Loading page ...

Study Guide1.6Pasteurellas–Small and Non-Motile BacteriaPasteurellas belong to the familyPasteurellaceae. These bacteria aresmall in sizeandnon-motile,which helps distinguish them from vibrios and enterobacteria.Important members includePasteurella,Haemophilus, andActinobacillus.•Haemophilus influenzaecan causemeningitis in children•Pasteurella multocidacausescholera in birds1.7Sulfur Bacteria–Recyclers of SulfurSulfur bacteria usesulfur or sulfur compoundsas electron acceptors in their metabolism. Duringgrowth, they producehydrogen sulfide, which causesstrong, unpleasant odorsin water and mud.Species ofDesulfovibrioare especially important in thesulfur cycle. They convert sulfur into formsthat plants can use to makesulfur-containing amino acids.1.8Bacteroides–Important AnaerobesBacteroides areanaerobic, Gram-negative bacteriawith unique movement and flagella patterns.Some species helpdigest cellulose in the rumen of cows, allowing plant material to be brokendown. Large numbers of Bacteroides are also found inhuman feces, where they may aid digestion.However, one species,Bacteroides fragilis, can causeserious blood infectionsin humans.1.9Veillonella–Gram-Negative CocciVeillonella species areanaerobic, Gram-negative diplococci. They are part of thenormal floraofthe mouth and digestive tract and are commonly found indental plaque.Although usually harmless, these bacteria can sometimes causeinfections of the femalereproductive tract.1.10Gliding Bacteria–Movement Without FlagellaSome bacteria move byglidingrather than using flagella. They secrete a slimy layer and move usingwave-like contractionsof their outer membranes.

Microbiology - The Bacteria - Page 4 preview image

Loading page ...

Study GuideExamples includeCytophagaandSimonsiella.Two important gliding bacteria,BeggiatoaandThiothrix, live in sulfur-rich environments. They breakdownhydrogen sulfideand release sulfur as visiblesulfur granules, playing a key role insulfurrecyclingin soil and water. These bacteria areGram-negative.1.11Myxobacteria–Bacteria With a Life CycleMyxobacteria areGram-negative, aerobic, gliding rodswith a unique developmental process.When nutrients become scarce, the cells gather together and form afruiting body. A stalk develops,and cells at the top change intoresistant, cyst-like structuresthat can survive harsh conditions.1.12Sheathed Bacteria–Protected FilamentsSheathed bacteria arefilamentous bacteriasurrounded by a protectivesheath made ofpolysaccharides and lipoproteins.This sheath helps the bacteriaattach to surfacesand protects them from environmental damage.The genusSphaerotilusis an example of this group.1.13Photoautotrophic Bacteria–Using Sunlight for EnergyPhotoautotrophic bacteria areGram-negative rodsthat obtain energy fromsunlightthroughphotosynthesis.•Anoxygenic photoautotrophsgrow only in anaerobic conditions and donot produceoxygen•Oxygenic photoautotrophs, calledcyanobacteria, use water as a hydrogen source andrelease oxygenCyanobacteria containchlorophylland carry out photosynthesis similar to plants and algae.Their cells containthylakoids, which are flat membranes holding photosynthetic pigments. They alsoformheterocysts, specialized cells that help innitrogen fixation.

Microbiology - The Bacteria - Page 5 preview image

Loading page ...

Study Guide1.14Chemoautotrophic Bacteria–Energy From ChemicalsChemoautotrophic (orchemolithotrophic) bacteria obtain energy frominorganic chemicalreactionsinstead of sunlight.•Some usecarbon dioxideas a carbon source•Thiobacillusspecies metabolize sulfur compounds•NitrosomonasandNitrobacteruse nitrogen compounds•Others usehydrogen gas,iron, ormanganeseThese bacteria are commonly found insoil and water, not inside the human body, and are known fortheirunusual biochemical processes.2.Gram-Positive BacteriaGram-positive bacteria have athick cell wallthat helps them retain the purple stain during Gramstaining. They come in different shapes and have important roles in health, disease, and industry.2.1Streptococci–Chain-Forming CocciStreptococci arespherical (coccus-shaped) bacteriathat divide in one direction, formingchains.They areGram-positive, and some species require oxygen (aerobic), while others grow withoutoxygen (anaerobic).When grown onblood agar, streptococci are classified by how they affect red blood cells:•Alpha-hemolytic: partially destroy red blood cells•Beta-hemolytic: completely destroy red blood cells•Gamma-hemolytic: do not destroy red blood cellsDifferent species cause different effects:•Streptococcus pneumoniaecausessecondary bacterial pneumonia•Streptococcus pyogenescausesstrep throatandrheumatic fever•Some species contribute todental cavitiesNot all streptococci are harmful. Certain harmless strains are used to makeyogurt, buttermilk, andcheese.

Preview Mode

This document has 14 pages. Sign in to access the full document!

Report

Microbiology - The Bacteria

Study Now!

Document Details

Related Documents

Microbiology - The Viruses

Microbiology - The Unicellular Algae

Microbiology - The Protozoa

Microbiology - The Immune System

Microbiology - The Host Parasite Relationship

Microbiology - The Fungi

Microbiology - The Development of Infectious Disease

Microbiology - The Chemical Basis of Microbiology

Microbiology - Soil Microbiology

Microbiology - Prokaryotes and Eukaryotes

Company

Explore

Study Tools