chapter 5 - the microbial world
TRANSCRIPT
CHAPTER 5
CHAPTER 5THE MICROBIAL WORLD
Prokaryotes
ProkaryotesStructurally simpleHave a great range of metabolic activities
Prokaryotesthree main shapes: spheres, rods and spiral (coccus, bacillus, spirillum)
ProkaryotesStudy of bacteria is known as bacteriology, a branch of microbiology
Archaea
ArchaeaGroup of single-celled microorganismsAmong the simplest, most primitive forms of lifeNo cell nucleus or organelles
ArchaeaArchaeon: an individual or species from the domain ArchaeaSome types of archaea were recently discovered at extreme temperatures around hydrothermal vents were thought to only be extremophilesCommon in marine environments, including sediment
Prokaryote Metabolism
Prokaryote MetabolismMetabolism: All the chemical reactions that take place inside an organism
Prokaryote MetabolismAutotrophs are primary producers which make their own organic compoundsPhotoautotrophsChemoautotrophs
Photoautotrophsmake organic compounds using photosynthesiscontain chlorophyll and other photosynthetic pigments
PhotoautotrophsPhotosynthesis occurs within the folded membranes of the bacterial cellNo chloroplastsAccounts for much of the primary production in open-ocean areas
ChemoautotrophsGain energy from chemical compounds instead of from lightIncluding hydrogen sulfide (H2S) and other sulfur, nitrogen and iron compounds
Heterotrophs obtain energy from respirationsome use aerobic and some use anaerobic respiration
HeterotrophsAnaerobic bacteria do not grow when oxygen is present and thrive when oxygen is absentEspecially in sediments deprived of oxygen (anoxic)
Unicellular Algae
Unicellular AlgaeAlgae: (s. alga) are a very diverse group of simple, mostly aquatic, mainly photosynthetic organisms
Unicellular AlgaeEukaryoticPhotosynthesis occurs in chloroplastsColor results from pigments and their concentrationsRange in size and complexity
Unicellular AlgaeAlgae lack true roots, stems, and leavesMulticellular seaweeds are considered protists, because they lack the specialized tissues of plants
Diatoms and Dinoflagellates
DiatomsUnicellular, many aggregate into chains or star-shaped groupsround, two-piece frustule: glassy shellDiatom cells are enclosed by cell walls made mainly of silica (SiO2)allows light to pass through so golden-brown chloroplasts can capture light energy for photosynthesis
DiatomsMany frustules have intricate perforations or ornaments such as spikes or spinesperforations allow gases and nutrients to pass in and outTheir sinking is often slowed by oil present in their cells or in the spines of the frustuleCarotenoids give diatoms their characteristic yellow-brown color
DiatomsThe frustules of dead diatoms contribute to biogeneous sediment known as diatomaceous oozeThis siliceous material or diatomaceous earth is mined and used in products for filtering swimming pools, clarifying beer, and mild abrasives in toothpaste
Dinoflagellates1,200 living speciesImportant primary producersPossess 2 flagellaOne along the groove in the centerOne floating along freely
DinoflagellatesMost have a cell wall armored with plates made of cellulose called a thecaMost photosynthesizeMany also ingest food particlesA few have a light-sensitive spot that acts as a crude eye
Algal BloomsSometimes form blooms that color the water red, yellow or another unusual shadeAlgal bloom: a rapid, sudden growth in the number of algae
Algal BloomsUnder favorable conditions, dinoflagellates can divide every 8-12 hoursSome dinoflagellates use bioluminescence - emit light
Red TideSome release toxic substances and seafood collected during these red-tide periods may be poisonouscertain dinoflagellates produce a neurotoxins called saxitoxin and brevetoxinconcentrated in the tissues of filter feeders such as clams and mussels
Red Tide when these shellfish are consumed by humans and they ingest high concentrations of brevetoxin or saxitoxin, paralytic shellfish poisoning (PSP)resultsin severe cases death can result in 12-24 hours
Red Tidesaxitoxin is over 100,000 times more potent than cocaine and concentrations sufficient to cause poisoning may be present in shellfish when red tide is not noticeable
Red Tide
Red Tide
Zooxanthellae
ZooxanthellaeZooxanthellae: A group of round, golden-brown dinoflagellates that live in close proximity to animals
ZooxanthellaeAnimals that harbor zooxanthellae include sponges, sea anemones, and giant clams
Other Unicellular Algae
Other Unicellular AlgaeThree additional groups are very significant primary producersAll three groups are so small 100s could fit inside a large diatom or dinoflagellate cell
Other Unicellular Algae1. SilicoflagellatesCharacterized by a star-shaped internal skeleton made of silica and two flagella of different lengthsCan be used to date sediment
Other Unicellular Algae2. CoccolithophoridsFlagellated, spherical cells Covered with button-like ornamental structure Coccoliths may be found in sediment as fossils
Other Unicellular Algae3. CryptophytesHave two flagella and lack a skeletonHave a chloroplast
Protozoans
ProtozoansProtozoan - structurally simple and very diverse eukaryotic organisms that are traditionally considered animal-like
ForaminiferansForaminiferans: often called forams, are marine protozoans that usually have a shell or test made of calcium carbonateHave long, thin, retractable pseudopodia (false feet), extensions of the cytoplasmMost live on the ocean bottom either free or attached
ForaminiferansForaminiferan Ooze: A form of calcareous ooze consisting mainly of the shells of deceased forams
ForaminiferansShells of warm water species are larger and more porous than those from colder watersdistribution of shells can be used to determine past water temperaturesGood indicator of the right type of environment for the formation of oil and the age of the sediment
Radiolariansradiolarians: Planktonic marine protozoans that secrete elaborate and delicate shells made of glass (silica) and other materials
RadiolariansTypical shells are spherical with radiating spinesThin needle like pseudopodia capture food particles, like forams
RadiolariansMicroscopic but form large colonies that reach 3m (9ft) in lengthInhabit open oceans
CiliatesCiliates: Protozoans with many hair-like cilia used in locomotion and feeding
CiliatesA familiar ciliate is the paramecium - freshwaterMany ciliates live in unusual places On the gills of clams, intestines of sea urchins, or the skin of fish
Fungi
FungiFungi: eukaryotic and mostly multicellular plant-like heterotrophsMolds and yeasts - unicellularAt least 500 species of marine fungimostly microscopic
FungiImportant decomposersMany are parasiticSome are symbiotic, such as lichensLichen provides support, plant provides food