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