General Microbiology Exam 1 Question and Answers

General Microbiology Exam 1 Question and Answers Microbes organisms and acellular entities too small to be clearly seen by the unaided eye simple in their construction and lack highly differentiated cells and distinct tissues 3 domains of microbes Bacteria (true bacteria), Archaea, Eukarya (eukaryotes) classified based on comparison of ribosomal RNA; affected by detailed structure of cells, biochemical/physiological characteristics, genetic sequencing Domain Bacteria singe-celled, cell wall with peptidoglycan, lack a membrane-bound nucleus, ubiquitous and some live in extreme enviornment cyanobacteria produce significant amounts of oxygen Domain Archaea unique rRNA gene sequences, lack peptidoglycan in cell walls, unique membrane lipids, unusual metabolic characteristics, many live in extreme enviornments Protists Domain Eukarya- generally larger than Bacteria and Archaea algae, protozoa, slime molds, water molds Fungi (saprophytic) yeast-unicellular mold-multicellular Viruses smallest of all microbes, requires host cell to replicate, cause range of diseases (some cancers) Viroids and Virusoids Infectious agents composed of RNA Virions infectious proteins Ribozymes RNA molecules that form peptide bonds, perform cellular work and replication Earliest Molecules may have been RNA surrounded by liposomes RNA Cellular pool of RNA exists in and associated with the ribosome (rRNA, tRNA, mRNA) catalytic in protein synthesis may be precursor to double stranded DNA can regulate gene expression ATP (adenosine 5' triphosphate) energy currency and is a ribonucleotide Earliest Metabolism energy sources under harsh conditions (inorganics) photosynthesis- cyanobacteria (2.5 billion years ago) and stromatolites Stromatolites mineralized layers of microorganisms Universal Phylogenetic tree based on comparisons of small subunit rRNA (SSU rRNA) aligned rRNA sequences from diverse organisms are compared and differences counted to derive a value of evolutionary distance determines RELATEDNESS, not time of divergence Last Universal Common Ancestor (LUCA) the root or origin of modern life is on a bacterial branch archaea and eukarya evolved independently of Bacteria archaea and eukaya diverged from common ancestry Endosymbiotic Hypothesis Origins of mitochondria, chloroplasts, and hydrogenosomes from endosymbiont mitochondria and chloroplasts- SSU rRNA genes show bacterial lineage, Hydrogenosomes anaerobic endosymbiont Cellular microbe diversity mutation of genetic material led to selected traits- new genes and genotypes evolved bacteria and archaea increase genetic pool by horizontal gene transfer within the same generation Strains Bacteria and archaea do not reproduce sexually consists of a descendents of a single, pure microbial culture (may be biovars, serovars, morphovars, pathovars) Binomial nomenclature genus and species epithet- Bacillus subtilus Microbiology Study of microorganisms Tools used to study microorganisms microscopes, culture techniques, molecular genetics, genomics Antony van Leeuwenhoek first person to observe and describe microorganisms accurately Spontaneous generation idea that living organisms can develop from nonliving or decomposing matter Francesco Redi discredited spontaneous generation showed that maggots on decaying meat came from fly eggs John Neddham mutton broth experiment (boiled and sealed) results: broth became cloudy and contained microorganisms Lazzaro Spallanzani Broth in flasks, first sealed then boiled results: no growth of microorganisms Louis Pasteur Swan-neck flask experiments created flasks with long, curved necks and boiled solutions, left flasks exposed to air results: no growth of microorganisms demonstrated microorganisms carried out fermentations (helped french wine industry)- developed pasteurization John Tyndall demonstrated that dust carries microorganisms; if dust was absent, nutrient broths remained sterile even when exposed to air also provided evidence of the existence of heat-resistant forms of bacteria Ferdinand Cohn heat-resistant bacteria could produce endospores 4 bodily-fluid "humors" blood, phlegm, yellow bile and black bile infectious disease first believed to be due to these imbalances Miasma poisonous gas; turning point in determining the causes of infectious diseases Agostini Bassi showed that a disease of silkworms was caused by a fungus (how to stop the disease without killing the microbe) this began microbiology M. J. Berkeley demonstrated that the great Potato Blight of Ireland was caused by a water mold Heinrich de Bary showed that smut and rust fungi caused cereal crop diseases Joseph Lister provided indirect evidence that microorganisms were the causal agents of disease; developed system of surgery (phenol), just wanted people to wash their hands! Robert Koch established the relationship between Bacillus anthracis and anthrax Koch's postulates used to establish the link between a particular microorganism and a particular disease Limitations of Koch's Postulates some orgnaims cannot be grown in pure culture (can only isolate 1% on plates) using humans is unethical Molecular and genetic evidence may replace and overcome these limits Dvelopment of Techniques Koch's work led to discovery of agar (instead of gelitin), petri dishes, nutrient broth and nutrient agar (growth medium), methods for isolating microorganisms (just added blood) Charles Chamberland developed porcelain bacterial filters to study tobacco mosaic disease- determined that infectious agents were smaller than bacteria and passed through filters (viruses) Pasteur and Roux discovered that incubation of cultures for long intervals between transfers caused pathogens to lose their ability of cause disease (attenuation) Attenuation pathogens that lose their ability to cause disease Immunology study of host defenses Edward Jenner used a vaccination procedure to protect individulas from smallpox Emil von Behring and Kitasato developed antitoxins for diphtheria and tenaus, evidence for humoral (antibody-based) immunity Elie Metchnikoff discovered bacteria-engulfing, phagocytic cells in blood, evidence for cellular immunity (developed immunology) Winogradsky and Beijerinck studied soil microbes and discovered interesting metabolic processes (nitrogen fixation); pioneered the use of enrichment cultures and selective media Basic aspects concerned with individual groups of microbes, microbial physiology, genetics, molecular biology and taxonomy Applied Aspects concerned with practical problems (disease, water, food, industrial microbiology) Molecular and Genomic methods led to second golden age of microbiology restriction enodnucleases, first novel recombinant molecule, DNA sequencing methods, bioinformatics and genomic sequencing and analysis Cocci spheres- promotes survival diplococci pairs steptococci chains staphylococci grape-like clusters tetrads 4 cocci in a square sarcinae cubic configuration of 8 cocci bacilli rods coccobacilli-very short rods vibrios resemble rods, comma shaped spirilla rigid helices spirochetes flexible helices mycelium network of long, multinucleate filaments pleomorphic organisms that are variable in shape plasma membrane selectibely permeable barrier, mechanical boundary of cell, nutrient and waste transport, location of many metabolic processes (respiration, photosynthesis), detection of environmental cues for chemotaxis gas vacule an inclusion that provides buoyancy for floating in aquatic environments Ribosomes protein synthesis Inclusions Storage of carbon, phosphate, and other substances Nucleoid localization of genetic material (DNA) Periplasmic Space in typical gram-negative bacteria, contains hydrolytic enzymes and binding proteins for nutrient processing and uptake in typical gram-positive bacteria, may be smaller or absent