Chapter 5Chapter 5

The Microbial WorldThe Microbial World

VirusesViruses

•• NonNon--cellular infectious agents that have cellular infectious agents that have two basic characteristics:two basic characteristics:–– Not capable of reproduction without a host Not capable of reproduction without a host

cellcell

–– Structure: Structure: •• Nucleic acid coreNucleic acid core-- can be DNA or RNAcan be DNA or RNA

•• Capsid (Protein coat)Capsid (Protein coat)-- consists of numerous protein subunits consists of numerous protein subunits organized into rodorganized into rod--like or many sided shape. Protein coat like or many sided shape. Protein coat also contains specific proteins that bind with receptors on also contains specific proteins that bind with receptors on host cells (great at mimicry!!) Many glycoprotein spikes host cells (great at mimicry!!) Many glycoprotein spikes extend from coatextend from coat--these spikes mutate so frequently that our these spikes mutate so frequently that our immune system cannot keep up.immune system cannot keep up.

VirusesViruses

•• Viruses in the Marine Community:Viruses in the Marine Community:

–– They are common in marine watersThey are common in marine waters

–– They can infect bacteria, plankton, fish, sea They can infect bacteria, plankton, fish, sea

turtles and marine mammalsturtles and marine mammals

–– Lysis (bursting) of viral infected cells spills Lysis (bursting) of viral infected cells spills

contents and releases large amounts of contents and releases large amounts of

organic matter that can be utilized by other organic matter that can be utilized by other

organisms (dissolved organic matter or DOM)organisms (dissolved organic matter or DOM)

ProkaryotesProkaryotes

•• Archea and BacteriaArchea and Bacteria

•• Characteristics of Archean and Bacterial Cells:Characteristics of Archean and Bacterial Cells:

–– ProkaryoticProkaryotic-- no nucleusno nucleus

–– Single chromosome (normally circular)Single chromosome (normally circular)-- some also some also

with plasmidswith plasmids

–– Most with cell wallMost with cell wall

–– Great metabolic diversityGreat metabolic diversity

ProkaryotesProkaryotes

•• Archea Archea ––

–– Ancient organisms Ancient organisms –– fossils found that date fossils found that date back 3.8 billion yearsback 3.8 billion years

–– Some live in very extreme environmentsSome live in very extreme environments

–– Variety of metabolic typesVariety of metabolic types

–– Widely distributed in the marine communityWidely distributed in the marine community

–– They can tolerate wide ranges in temperature, They can tolerate wide ranges in temperature, salinity and even desiccation (drying out)salinity and even desiccation (drying out)

–– Can be found in many areas including near Can be found in many areas including near hydrothermal vents and salt flats (two very hydrothermal vents and salt flats (two very extreme environments)extreme environments)

ProkaryotesProkaryotes

•• Special Features of Bacteria:Special Features of Bacteria:

•• A variety of shapes including spirals, A variety of shapes including spirals, spheres, rods and rings spheres, rods and rings

•• Cell wall structure is semiCell wall structure is semi--rigid, but rigid, but permeable; most with cell wall permeable; most with cell wall

•• Size is normally microscopic, but a few are Size is normally microscopic, but a few are largelarge

•• Wide variety of metabolic typesWide variety of metabolic types

•• Very abundant worldwideVery abundant worldwide

Aerobic respiration

ProkaryotesProkaryotes

•• Metabolic diversity:Metabolic diversity:

•• Photosynthesis Photosynthesis –– derive energy from lightderive energy from light

•• Chemosynthetic Chemosynthetic –– derive energy from derive energy from

chemical compoundschemical compounds

•• Heterotrophs Heterotrophs –– derive energy from organic derive energy from organic

matter by respirationmatter by respiration

Prokaryote metabolic diversity• Heterotrophic microbial metabolism• Fermentation

• Special metabolic properties– Methylotrophy

– Syntrophy• Anaerobic respiration

– Denitrification - nitrate as electron acceptor– Sulfate reduction - sulfate as electron acceptor

• Electron donors• Energy for reduction

– Acetogenesis - carbon dioxide as electron acceptor– Other inorganic electron acceptors

– Organic terminal electron acceptors• Chemolithotrophy

– Hydrogen oxidation

– Sulfur oxidation– Ferrous iron (Fe2+) oxidation

– Nitrification– Anammox

• Phototrophy

Dissolved organic carbon in the ocean

• Forms polymers and particles (snow) that

are the habitat for many prokaryotes in the water column

Carbon in the ocean (gigatons)

39973

150sediment

38100deep ocean

1020surface ocean

700dissolved organic

3organisms

Transparent exopolymers

• Recall that there are 700 gigatons of

dissolved organic compounds in the ocean

Transparent exopolysaccharides(TEP)

Marine snowPhytoplankton

• Unicellular algae and cyanobacterial

component of the plankton

• 50% of global photosynthesis

• Some major algal groups

– Diatoms

– Dinoflagellates

– coccolithophores

Global primary production DiatomsDiatoms

•• Diatoms:Diatoms:

–– Photosynthetic Photosynthetic

–– YellowYellow--brown color in life is a result of brown color in life is a result of

photosynthetic pigments, chlorophyll A and C photosynthetic pigments, chlorophyll A and C

and carotenoidsand carotenoids

–– Shell of silica called a frustule Shell of silica called a frustule

–– Most important primary producer on Earth Most important primary producer on Earth

–– Mostly solitary and unicellularMostly solitary and unicellular

–– Some can form coloniesSome can form colonies

DiatomsDiatoms

•• DiatomsDiatoms

–– Around half of the 12, 000 known species are marineAround half of the 12, 000 known species are marine

–– Most are planktonicMost are planktonic

–– Store excess energy as an oil which also aids in Store excess energy as an oil which also aids in buoyancybuoyancy

–– Tiny pores in shell used for gas/nutrient exchangeTiny pores in shell used for gas/nutrient exchange

DinoflagellatesDinoflagellates

•• DinoflagellatesDinoflagellates–– Most species live in marine environmentMost species live in marine environment

–– Mostly photosynthetic, some can ingest particlesMostly photosynthetic, some can ingest particles

–– Each species has unique shape reinforced by plates Each species has unique shape reinforced by plates of polysaccharide (like cellulose)of polysaccharide (like cellulose)

–– Two flagella in grooves on body that produce motionTwo flagella in grooves on body that produce motion

–– Some are bioluminescent (read Some are bioluminescent (read ““Bay of FireBay of Fire”” on pg. on pg. 96)96)

• Ceratium-dinoflagellatesDinoflagellates occur in enormous numbers in the ocean, particularly in tropical waters and display a huge diversity of form. The large protrusions seen on this

Ceratium-dinoflagellate are used for protection against predators.

DinoflagellatesDinoflagellates

•• DinoflagellatesDinoflagellates

–– Zooxanthellae are important dinoflagellates Zooxanthellae are important dinoflagellates

that live in a symbiotic relationship with corals, that live in a symbiotic relationship with corals,

sea anemones and other organisms (many of sea anemones and other organisms (many of

these host organisms have little or no growth these host organisms have little or no growth

without their symbiotic partner)without their symbiotic partner)

Algal BloomsAlgal Blooms

•• Diatoms and dinoflagellates can go Diatoms and dinoflagellates can go

through periods of rapid growth known as through periods of rapid growth known as

““bloomsblooms””

•• This is a result of high levels of nutrients in This is a result of high levels of nutrients in

the waterthe water

•• These blooms can be harmful to marine These blooms can be harmful to marine

organisms and even people at timesorganisms and even people at times

Algal bloom southern England Coccolithophore bloom Bering Sea

Red tides - dinoflagellatesDinoflagellatesDinoflagellates

–– A few species lack chloroplasts and live as parasites A few species lack chloroplasts and live as parasites in marine organismsin marine organisms

–– Some species can reproduce in larger numbers and Some species can reproduce in larger numbers and produce produce ““Red TideRed Tide”” (read (read ““Red Tides and Harmful Red Tides and Harmful Algal Blooms, pg. 338)Algal Blooms, pg. 338)

–– PfiesteriaPfiesteria is a dinoflagellate that produces very is a dinoflagellate that produces very serious toxins that can cause massive fish kills, harm serious toxins that can cause massive fish kills, harm shellfish and impair the nervous system in humans.shellfish and impair the nervous system in humans.

–– PfiesteriaPfiesteria was discovered near the Outer Banks in was discovered near the Outer Banks in North CarolinaNorth Carolina

–– CoccolithophoresCoccolithophores

•• Ornate shells of calcium carbonateOrnate shells of calcium carbonate

ProtozoaProtozoa

•• Foraminiferans (forams) Foraminiferans (forams)

–– Exclusively found in marine communityExclusively found in marine community

–– Found on sandy or rocky bottoms Found on sandy or rocky bottoms

–– Shells of calcium carbonateShells of calcium carbonate

–– Can be important contributors of calcareous Can be important contributors of calcareous

material on coral reefs or sandy beachesmaterial on coral reefs or sandy beaches

–– Pseudopods (false feet) extend through pores Pseudopods (false feet) extend through pores

in the shell where they are used to capture in the shell where they are used to capture

minute food particles such as phytoplanktonminute food particles such as phytoplankton

ProtozoaProtozoa

•• RadiolariansRadiolarians

–– Planktonic, mostly microscopic, although a Planktonic, mostly microscopic, although a

few can reach large sizesfew can reach large sizes

–– Shell of silicaShell of silica

–– Like forams, they use pseudopods that extend Like forams, they use pseudopods that extend

through pores in the shell where they are through pores in the shell where they are

used to capture minute food particles such as used to capture minute food particles such as

phytoplanktonphytoplankton

ProtozoaProtozoa

•• CiliatesCiliates

–– Cilia present for locomotionCilia present for locomotion

–– Most live as solitary cellsMost live as solitary cells

–– Some build shells made of organic Some build shells made of organic

debrisdebris

–– May live on hard substrateMay live on hard substrate

–– Some are Some are planktonicplanktonic

FungiFungi

•• Eukaryotic and mostly multicellularEukaryotic and mostly multicellular

•• HeterotrophicHeterotrophic

•• Most of the 1500 species of marine fungi Most of the 1500 species of marine fungi

are microscopicare microscopic

FungiFungi

•• Like bacteria, many fungus break down Like bacteria, many fungus break down dead organic matter into detritusdead organic matter into detritus

•• Some fungus live in symbiosis with Some fungus live in symbiosis with cyanobacteria, these are known as lichenscyanobacteria, these are known as lichens

•• Marine lichens often live in waveMarine lichens often live in wave--splashed splashed areas of rocky shorelines and other hard areas of rocky shorelines and other hard substrate substrate