Difference between revisions of "H. influenzae"
|Line 75:||Line 75:|
[[Category:Pages edited by students of Doreen Cunningham at Saint Augustine's College]]
[[Category:Pages edited by students of Doreen Cunningham at Saint Augustine's College]]
Latest revision as of 18:37, 7 September 2011
Haemophilus influenzae is found along the bacteria lineage: kindgom name:Bacteria, phylum name:Proteobacteria,class name:Gamma Proteobacteria;order:Pasteurellales, family name:Pasteurellaceae; and genus name Haemophilus. the specie name is haemophilus influenzae
hamophilus influenzae has other names by which it can be identifed as it was formely known as the Pfeiffer's bacillus or Bacillus influenzae. it is also known as haemophilus meningitidis,Mycobacterium influenzae,Influenza-bacillus to name a few.
other species that fall under the same genus name are: haemophilus ducreyi and haemophilus influenzae aegyptius
Description and Significance
Haemophilus influenzae is a small Gram negative bacillus which grows best at 35-37 degrees Celsius and at a pH of 7.6. the bacteria has specific need required for growth which are hemin(factor X) and nicotinamide adenine dinucleotide (NAD+:factor V). the growth of the bacteria is enhanced by high concentrations of CO2 concentrations. the haemophilus influenzae bacteria causes clinical symptoms based on the presence of the bacterial capsule. it is the main cause of meningitis in children 6 months to 5 years. Haemophilus influenzae type b, or Hib, is a bacterium estimated to be responsible for some three million serious illnesses and an estimated 386 000 deaths per year, chiefly through meningitis and pneumonia.(WHO, December 2005). Due to its invasive nature the organism enters the circulation and crosses the blood-brain barrier, resulting in a rapidly progressing meningitis (stiff neck), convulsions, coma and death. the general habitat of the H. influenzae are the mucous membranes of the respiratory tract in humans and the transmition of the bacteria from person to person occurs by close contact and sneezing.
Describe the size and content of the genome. How many chromosomes? Circular or linear? Other interesting features? What is known about its sequence?
Haemophilus influenzae is a non-motile Gram-negative coccobacillus first identifed by Dr. Robert Pfeiffer in 1892. the genome structure of haemophilus influenzae consist of 1,830,138 nucleotide base pairs and it is estimated to have approximately 1740 genes and was the first genome to be sequenced and assembled in a free living organism (Fleischmann RD et al). It consist of a single circular chromosome replicon which has coding regions for rRNA, tRNA and proteins. They identified that the four nucleotides are not used at equal frequency across the genome as A and T are more common than C and G. there are sequence uncertainties in the genome as other symbols occur in the sequence and corresponds to positions in the sequence that are not clearly one base or another. other bases which are seen in the sequence are Y, R, K, M, S, W and N. (Computational Genomics). because bacteria can transfer DNA from one specie to another by horizontal gene transfer, haemophilus influenzae takes up DNA by recognizing a 9- base pair sequence, 5'-AAGTGCGGT which is carried in multiple copies in its chromosome. there are 1465 copies of the 9-base pair DNA uptake sequence.the aligning of theses 9-base pair sequence sites have shown that there is an extended consensus region within the DNA of 29 base pairs containing the core 9-base pair region and also two 6-base pair A-T rich regions, each spaced one helix turn apart. most of the sites are inverted repeats(IR) located downstream to a gene terminus and are thus capable of forming loop structures in mRNA that signals for termination of transcription.(Smith OH, 1995 Jul 28;269(5223):538-40).
Cell Structure, Metabolism and Life Cycle
Interesting features of cell structure; how it gains energy; what important molecules it produces.
haemophilus influenzae is a bacteria and thus exhibits characteristics of a prokaryotic cell. it was identified as a gram negative bacteria because of its response to Gram staining techniques, as it stains red. the gram negative coccobacillus has important cell wall components that play a role in its survival and its pathogenicity. H. influenzae bacteria consist of various strains based on the presence or absence of an outer covering called capsules. Haemophilus influenzae, the major pathogen, can be separated into encapsulated or typable strains, of which there are seven types (a through f including e') based on the antigenic structure of the capsular polysaccharide, and unencapsulated or nontypable strains (Baron S). by isolating H. influenzae it was observed that some were shown to have pili structures, which aid in attachment to the oropharyngeal epithelial cell of humans. another important feature of the H. influenzae cell structure is the rough lipopolysaccharide(LPS) which extends from the cell surface. there are variations in the LPS from specie to specie and its has been suggested to be important in the life cycle of the Haemophilus influenzae.
haemophilus influenzae metabolizes sugar as its source of energy, however there is little known about this metabolic capability of the H. influenzae. it is a facultative anaerobe and thus makes ATP by aerobic respiration when oxygen is present and is also capable of metabolizing its sugar source in the absence of oxygen by fermentation. it was found that over 90% of H. influenzae isolated, breaks down sugars such as maltose glucose, galactose and ribose by fermentation and the remaining percent ferment fructose, mannose, or glycerol.
haemophilus influenzae reproduces by a asexual process called binary fission which is characteristic to bacteria. during binary fission, the H. influenzae begins replication at the origin of replication site. as the chromosome is replicated, proteins aid in the movement of the chromosome to opposite poles of the cell and the elongation of the cell. septum formation and invagination of the cell membrane separates the chromosomes into two separate cells that are capable of growing to the size of the original parent cell.
Ecology and Pathogenesis
H. influenzae bacteria is able to coexist with the human host and the devastating results associated with the disruption of the delicate state of balanced pathogenesis resulting in both acute and chronic respiratory tract infections. the H. influenzae is able to live as a commensal disease in the human body, however when certain conditions exist, the bacteria is able to leave the bloodstream and travel to the brain where it causes meningitis. (1) Meningitis is a bacterial infection of the membranes covering the brain and spinal cord. respiratory tract infections associated with nontypeable H. influenzae are a major cause of morbidity and mortality in both developed and undeveloped countries. the success of this organism as a colonizer and pathogen is due to its lack of reliance on any single mechanism of attachement and its ability to respond rapidly to host defense mechanisms by antigenic variation of proteins and enzymes.(1) infection and disease represents an imbalance of colonization which is due to the host the micro-environment and the organism. the Non typeable haemophilus influenzae(NTHi)attaches itself to the mucous membranes of extracellular matrix essential to allow the organism to multiply in a particular host, it also colonizes other tissue types. invitro studies suggest the NTHi adheres to repiratory epithelial cells that either lack cilia or are structurally damaged, which occurs as a result of numerous factors unrelated to the presence of bacteria. HMW1 and HMW2 proteins on NTHi strains bind mamalain surface structure containing glycoproteins related to heparan sulfate.(1) IgA is an extremely important antibody at all mucosal surface with the IgA1 being the dominant antibody in the upper respiratory tract. starins of H. inf;luenzae produce three types of IgA1 protease all of which cleave the heavy chain of IgA1 in the hinge region at one of several postproline sites. the IgA1 protease derived from H. influenzae are antigenically diverse. the function of the protease are clevage and adhesion. NTHi strains enter endothelial cells and penetrate the mucosal surface and demonstrate paracytosis which includes adherence to and passage through the lung epithelial cells.(1)
The H. influenzae bacteria live in the upper respiratory tract and are usually transmitted by close contact with an infected individual. Droplets in the air from a sneeze, cough, or close conversation can be inhaled and may also cause infection. the symptoms related to H influenzae virus in children include unusual irritability,difficulty sleeping or staying asleep,tugging or pulling at one or both ears,fever,fluid draining from ear(s).(8) these symptoms are normally seen in children suffering from otitis media (middle ear infection). for conjunctivitis infections which is an inflammation of the conjunctiva of the eye the symptoms related to this infection are redness, swelling, drainage from one eye or sometimes both, burning of eyes, and sensitive to brightness or light .meningitis infection are accompanied by neck and/or back pain,headache,nausea and vomiting, neck stiffness in children older than 1 year.(8)however symptom of meningitis in infants are harder to pinpoint and include irritability,sleeping all the time,refusing a bottle,cries when picked up or being held,inconsolable crying, ,bulging fontanelle (or soft spot) and behavior changes.(8) H. influenzae caused infections can be diagnosed by the examination of a culture of fluid from the eye, ear, throat, or spinal fluid. however other test such as a chest or neck x-ray or blood test can be used as a diagnosis. H influenzae infections are treated by the use of antibiotics, however the location of the infection determines how long the treatment is applied and also the severity of the infection.(8) effective vaccine development has help to abolish the H. influenzae type b in US. even with immunization with the vaccine children can still develop the infection.(8)
Computational Genomics: Example of sequence statistics and gene finding with MATLAB http://www.computational-genomics.net/case_studies/haemophilus_demo.html
1.A Ruth Foxwell, Jennelle M. Kyd and Allan W. Cripps. "Nontypeable Haemophilus Influenzae: Pathogenesis and Prevention". Microbiology and Molecular Biology Review. 1998 June; 62(2): 294-308.
2. Smith HO, Tomb JF, Dougherty BA, Fleischmann RD, Venter JC. "Frequency and distribution of DNA uptake signal sequences in the Haemophilus influenzae Rd genome". Department of Molecular Biology and Genetics, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA. Science.1995 Jul 28;269(5223):538-40.
3. Fleischmann RD, Adams MD, White O, Clayton RA, Kirkness EF, Kerlavage AR, Bult CJ, Tomb JF, Dougherty BA, Merrick JM. "Whole-genome random sequencing and assembly of Haemophilus influenzae Rd". Science. 1995 Jul 28; 269(5223):496-512.
4. JOSEPH W. ST. GEME III*tt, JEROME S. PINKNERt, GRAHAM P. KRASAN*, JOHN HEUSER§, ESTHER BULLITTr,ARNOLD L. SMITHII, AND Scorr J. HULTGRENt. "Haemophilus influenzae pili are composite structures assembled via the HifB chaperone" (October 1996).*Edward Mallinckrodt Department of Pediatrics, and Departments of tMolecular Microbiology and §Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO 63110; 1Department of Biophysics, Boston University School of Medicine, Boston, MA 02118; and IlDepartment of Molecular Microbiology and Immunology, University of Missouri, Columbia, MO 65203.Proc. Natl. Acad. Sci. USA Vol. 93, pp. 11913-11918, Microbiology
5.Dr Abdul Ghaffar. "BACTERIOLOGY - CHAPTER EIGHTEEN BORDETELLA, HAEMOPHILUS AND LEGIONELLA
6.Jeffrey N. Weiser."Relationship between Colony Morphology and the Life Cycle of Haemophilus influenzae: The Contribution of Lipopolysaccharide Phase Variation to Pathogenesis". The Journal of Infectious Diseases.Vol. 168, No. 3 (Sep., 1993), pp. 672-680 http://www.jstor.org/stable/30113433
7. Baron S. "Haemophilus Species".Medical Microbiology. 4th edition. Galveston (TX): University of Texas Medical Branch at Galveston; 1996. Chapter 30.
8. Children Hospital Boston. "Haemophilus Influenzae Infections". http://www.childrenshospital.org
9. ANU RAGHUNATHAN, NATHAN D. PRICE, MICHAEL Y. GALPERIN, KIRA S. MAKAROVA, SAMUEL PURVINE,ALEX F. PICONE,TIM CHERNY,TAO XIE,THOMAS J. REILLY,ROBERT MUNSON, JR. RYAN E. TYLER,BRIAN J. AKERLEY,ARNOLD L. SMITH,BERNHARD O. PALSSON,and EUGENE KOLKER. "In Silico Metabolic Model and Protein Expression of Haemophilus influenzae Strain Rd KW20 in Rich Medium". A Journal of Integrative Biology. Number 1, 2004, volume 8. Mary Ann Liebert, Inc.
10. NCBI taxonomy Browser. http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?lvl=0&id=727
Page authored by _Roxanne Smith____, student of Prof. Doreen Cunningham at Saint Augustine's College.