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MoBio_Presentation - Diversity and biogeography of...

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Unformatted text preview: Diversity and biogeography of bacterial assemblages in surface sediments across the San Pedro Basin, Southern California Borderlands by Ian Hewson, Myrna E. Jacobson/ Meyers and Jed Fuhrman Presented by: Jacob Pack Tu My To Background Information Sediment bact er ia play impor t ant r ole in ocean biogeochemical cycles L it t le known about bact er ial communit ies or t heir dist r ibut ion in coast al or shelf sediment s M ost st udies t o dat e ar e limit ed Gener al idea: fact or s of a r egion affect bact er ial composit ion Purpose of Study Under st and bact er ial assemblage dist r ibut ion acr oss San Pedr o Basin See if habit at specificit y exist s among t he communit ies Examine cor r elat ion bet ween habit at specificit y and ecosyst em funct ion Sample Collection 8 differ ent st at ions acr oss San Pedr o Basin 35 km of ocean floor , fr om Califor nia mainland t o Cat alina I sland Dept hs r anged fr om 27 t o 912 met er s Methods/Procedures Results Sampling Location Collect ed M ay 2004 8 sit es acr oss San Pedr o Basin Sediment s (t op 1 cm) collect ed for bact er ial/vir al analysis Determining Bacterial Abundance Ext r act ed samples ar e st ained wit h SYBR Gr een I Epifluor escence micr oscopy M agnified 1000x Used t o individually count cells Richness did not change much acr oss t he Basin Compar ison bet ween t wo differ ent envir onment s (mainland and Sant a Cat alina) Determining Bacterial Abundance 1 2 3 4 5 6 7 8 Alkaline Phosphatase Analysis H igh act ivit y = nut r ient deficiency/imbalance M et hylumbellifer one phosphat e was used t o measur e phosphat ase act ivit y 2 micr omolar concent r at ion Specific act ivit y = (phosphat ase act ivit y/micr obial abundance) Alkaline Phosphatase Analysis 1 2 3 4 5 6 7 8 Gener al decr ease in phosphat ase act ivit y fr om mainland t o Sant a Cat alina L it t le cor r elat ion bet ween phosphat ase act ivit y and bact er ial composit ion automated rRNA intergenic spacer analysis ARISA Used on ext r act ed DNA samples A specific DNA r egion is isolat ed and amplified wit h PCR Fr agment s ar e fluor escent ly t agged Run on polyacr ylamide gel; laser used automated rRNA intergenic spacer analysis ARISA Y-axis: peaks, in t er ms of fluor escence unit s Used for pr ofiling bact er ial communit y in a r egion A somewhat accur at e est imat ion, not always exact automated rRNA intergenic spacer analysis ARISA Fr om samples: Assemblages evenly disper sed bet ween st at ions Bact er ial composit ions bet ween sur face and deep sediment r emain differ ent L ocal select ivit y may occur t o give differ ent condit ions (i.e. mixing of wat er ) Results L it t le bact er ial abundance/r ichness/diver sit y Unexpect ed; envir onment al var iat ions exist bet ween deep and shallow sediment s I ndividual bact er ial communit ies differ ed fr om shallow t o deep wat er s envir onment al differ ences (i.e. wat er cur r ent mixing) Decr ease of phosphat ase act ivit y H igher nut r ient input s fr om coast M or e densit y and diver sit y of act ivit y along coast line t han in open ocean Discussion Even disper sion of sediment bact er ia over San Pedr o Basin suspended par t icles, fecal mat t er , animals, or t hr ough t he sediment layer it self Need t o know r elat ionship bet ween enzyme act ivit y, nut r ient availabilit y, and communit y st r uct ur e and funct ion Abundance/diver sit y: lit t le t o no change Composit ion of assemblages: dr amat ic changes ...
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