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1 Main points from last lecture 1. Differences between prokaryotes (Bacteria and Archaea) and eukaryotes 2. Differences among Bacteria, Archaea, and Eucarya: organelles, cell walls (peptidoglycan in bacteria), lipids (ester vs ether linkage) 3. Use of small subunit ribosomal RNA as phylogenetic marker (16S rRNA for prokaryotes) Properties Procaryotes Eucaryotes Groups Eubacteria, archaebacteria* Algae, fungi, protozoa, plants, animals Size Generally small, usually <2 um in diameter Usually larger, 2 to >100 um in diameter Nuclear structure and function: Nuclear membrane Nucleolus DNA Division Sexual reproduction Introns in genes Absent Absent Single molecule, not complexed with histones (other DNA in plasmids) No mitosis No meiosis Rare Present Present Present in several chromosomes, usually complexed with histones Mitosis; mitotic apparatus with microtubular spindle Meiosis Common Cytoplasmic structure and organization: Plasma membrane Internal membranes Ribosomes Respiratory system Photosynthetic pigments Cell walls Usually lacks sterols Relatively simple; limited to specific groups 70S in size Part of plasma membrane or internal membranes; mitochondria absent In organized internal membranes or chlorosomes; chloroplasts absent Present (in most) composed of peptidoglycan and other components Present (in some) Present (in some) Sterols usually present Complex; endoplasmic reticulum Golgi apparatus 80S, except for ribosomes of mitochondria and chloroplasts, which are 70S In mitochondria In chloroplasts Present in plants, algae, fungi; absent in animals, most protozoa; usually polysaccharide Absent Absent Endospores Gas vesicles Forms of motility: Flagellar movement Flagella; each flagellum composed of one flagella rotate Microtubules Absent fiber; Flagella or cilia; composed of microtubular elements arranged in characteristic pattern of nine outer doublets and two central singlets; do not rotate Widespread: present in flagella, cilia, basal bodies mitotic spindle apparatus, centrioles 2 a Main points, conti. 3 4. Dividing up microbes into functional groups • source of carbon: autotroph vs. heterotroph • source of energy: phototroph vs. chemotroph Chemoorganotroph= heterotroph 5. Eukaryotic microbes in various functional groups: primary producers, grazers, and mixotrophy. 6. Connection between phylogeny (“community structure”) and function (metabolism—what microbes do) is a big question in microbial ecology today. 4 Terms you need to learn (if you don’t know already) 1. DNA, protein 2. RNA: mRNA, tRNA, and rRNA 3. Ribosomes (proteins + rRNA) 4. Lipids (ester vs. ether) 5. Organelles: Nucleus, chloroplast, mitochondria CO2 Fish 20 Macrograzers (mesozooplankton) Micrograzers (protists) CO2 Big pools & fluxes High biomass Bacteria + NH4 , Fe DOM Large Small Phytoplankton CO2 Large organic carbon pool ca. 50% of primary production 21 What primary producers are in the oceans? What are the main types of phytoplankton? Early emphasis on “net phytoplankton” Big enough to catch with large nets Easily visible and distinguishable by light microscopy (electron microscopy needed for species level identification) Identifying features of algae 22 • Shape and Size • Pigments: many more than in land plants – All have chlorophyll a (chl a) used to estimate phytoplankton biomass – Anoxygenic photosynthesizing bacteria have bacteriochlorophyll a – Many (all?) have “accessory pigments”, which really are main light harvesting pigments – These pigments can be used to quantitatively estimate abundance of specific algal groups 22A Why so many different type of pigments Note “attenuation” (shading) at both ends of the spectrum 22B Very simple guide to photosynthesis Light Accessory PigmentsChlorophyll a Light Reactions Dark Reactions ATP and NADH CO2 CH2O 23 H2O O2 Some important eukaryotic algal groups: large or net phytoplankton 24 Division Common name Characteristic Pigments Chlorophyta green algae Chl b 13 Predecessor to chloroplast Phaeophyta brown algae chl c and fucoxanthin 99 Includes macroalgae (e.g. kelp) Rhodophyta red algae phycobilins 98 produce agar; few microbial representatives Chrysophyta (Bacillariophyceae)** diatoms chl c and fucoxanthin 50 Diatoms have Si in cell walls and often dominate spring blooms Chrysophyta (Coccolithophoridales) coccolithophorids chl c and fucoxanthin 90 Outer covering made of CaCO3 chl c; xanthophylls; phycoblins 60 Motility driven by flagella chl c and peridinin 93 some heterotrophic; red tide organisms Cryptophyta Pyrrhophyta dinoflagellates % Marine* Comments *% marine refers to their abundance in the oceans vs. freshwaters **There are other members of this division besides diatoms and coccolithophorids. 25 Division Common name Chrysophyta diatoms (Bacillariophy ceae) Characteristic Pigments chl c and fucoxanthin Comments Diatoms have Si in cell walls and often dominate spring blooms Chrysophyta (Coccolithophoridales) Coccolithophorids chl c and fucoxanthin Outer covering made of CaCO3 Pyrrhophyta dinoflagellates chl c and peridinin some heterotrophic; red tide organisms 26 Evidence that the oceans have more than just “net phytoplankton” • Lots of chlorophyll and 14CO2 fixation in <1 um size fraction • Epifluorescence counts of auto-fluorescencing cells • Cells were too small (ca. 1 um) and without internal structures, i.e. they are bacteria. (But there are some small eukaryotic phytoplankton— poorly understood. 27 Coccoid cyanobacteria are abundant and important in the oceans! 1. Well known in lakes and reservoirs 2.Importance in oceans discovered in 1980 (Synechococcus) and Prochlorococcus (1986) 3.Another important cyanobacterium: Trichodesmium 29 Some separate Prochlorococcus from “cyanobacteria” and equate “cyanobacteria” with Synechococcus, but not true Synechococcus and Prochlorococcus are both cyanobacteria and are distantly related Selected papers about marine coccoid cyanobacteria 30 Li, W. K. W. and others 1983. Autotrophic picoplankton in the tropical ocean. Science 219: 292-295. Chisholm, S. W., R. J. Olson, E. R. Zettler, R. Goericke, J. B. Waterbury, and N. A. Welschmeyer. 1988. A novel free-living prochlorophyte abundant in the oceanic euphotic zone. Nature 334: 340-343. Palenik, B. and others 2003. The genome of a motile marine Synechococcus. Nature 424: 1037-1042. Rocap, G. and others 2003. Genome divergence in two Prochlorococcus ecotypes reflects oceanic niche differentiation. Nature 424: 1042-1047. Waterbury, J. B., S. W. Watson, F. W. Valois, and D. G. Franks. 1986. Biological and ecological characterization of the marine unicellular cyanobacterium Synechococcus, p. 71-120. In T. Platt and W. K. W. Li [eds.], Photosynthetic Picoplankton. Department of Fisheries and Oceans. Schematic of epifluorescence microscope 31 Excitation light Dichroic mirror Ocular (10x): emission Objective (100X) Stage with sample 32 33 Sample is excited by lower wavelength light (say 400 nm) and the emitted light (“emission”) is at a higher wavelength (say 600 nm) Final magnification= 1000X 34 Autofluorescencing cells = autotrophs= phototrophs Must have pigment, with few exceptions Usually chlorophyll, but can excite different pigments with different wavelenghts of light Heterotrophic cells (heterotrophic bacteria) Need to add fluorogenic stain (DAPI and acridine orange) to stain DNA or other cellular material 35 Red color due to fluorescence from chl a 35A 36 Property Synechococcus Prochlorococcus Size 1.0 um 0.7 um Chlorophyll a Yes Modified Chlorophyll b No Yes Phycobilins Yes Less, variable Visible in microscope? Yes Difficult Habitat Widespread Open oceans 37 Biomass in North Pacific Gyre % of total Mixed Layer total water column (mgC/m2) Het. Bacteria 45 1273 45.4 Prochlorococcus 35 973 34.7 Synechococcus 2 58 2.1 Picoeukaryotes (< 3 um) 14 404 14.1 Large algae 4 98 3.5 Component Eukaryotes From Campbell et al. 1994 L&O Table 3. Comparison of mean abundance estimates and between-station variability for microbial populations in the HNLC equatorial Pacific, the low nutrient western equatorial Pacific (2°N to 2°S) and the oligotrophic subtropical Pacific (HOT). Abundance estimates are cells ml-1 from 050 m depth. Standard deviations (S.D.) and % coefficient of variations (C.V.) are for the mean estimates of population abundances averaged for the 0-50 m depth range at individual sampling stations. Cells per ml Region HNLC Equator Parameter Mean S.D. C.V. HBACT PRO SYN PEUK 716,000 126,000 18% 145,000 38,000 26% 9,800 3,400 35% 6,300 1,800 28% 172,000 72,000 42% 2,300 2,600 113% 870 450 51% 183,000 45,000 25% 1,700 1,100 65% 720 360 50% Western Equator Mean S.D. C.V. HOT Mean S.D. C.V. 444,000 119,000 27% HBACT=heterotrophic Bacteria; Pro=Prochlorococcus; Syn=Synechnococcus; PEUK=picoeukaryotes From Landry and Kirchman, DSR 2002 38 39 Numbers worth remembering Viruses: 107 ml-1 Heterotrophic Bacteria: 106 ml-1 Cyanobacteria: 105 ml-1 Protists (grazers): 104 ml-1 Large (>3 um) phytoplankton: 103 ml-1 40 In oligotrophic waters, coccoid cyanobacteria account for >90% of Phytoplankton biomass (chlorophyll a) Primary production 41 Global estimates: Roughly 50% of total marine primary production If marine is 50% of total production---> Cyanobacteria account for about 25% of global primary production!! 42 From Madigan et al. “Brock Biology of Microorganisms” 43 Another main type of cyanobacteria: Trichodesmium (formally known as Oscillatoria) Filaments of several cells, common in Sargasso Sea Can form macroscopic tuffs of cells Do NOT have heterocysts More about Tricho and heterocysts when we talk about N2 fixation. Other algae: note the weird and wonderful shapes! Not all algae are “nice”