25 Jun Based on my lectures and the assigned paper
Question
1) Based on my lectures and the assigned paper: Does the evidence suggest that peroxisomes were acquired at the same time and by the same mechanism as mitochondria and chloroplast? After you answer your question with a distinct Yes or No, THEN explain your answer. (10 points)
2) Why do peroxisomes from many different classes of organisms have similarcharacteristics? Be certain to include the evolutionary aspects in your answer – in fact this is the key point of this question so don’t digress too far from the key point. (8 points)
3) Why do peroxisome from many different classes of organisms have different characteristics? Be certain to include the evolutionary aspects in your answer – in fact this is the key point of this question so don’t digress too far from the key point. (5 points)
4) Is there a relationship between peroxisomes and the endoplasmic reticulum? First clearly answer Yes or No. THEN explain your answer. (5 points)
5) What role does removal of the cell wall have in the formation of the peroxisome when you consider this putative evolutionary process? (5 points)
.Peroxisome Diversity and Evolution
Author(s): Toni Gabaldón
Source: Philosophical Transactions: Biological Sciences, Vol. 365, No. 1541, Evolution of
Organellar Metabolism in Unicellular Eukaryotes (Mar. 12, 2010), pp. 765-773
Published by: The Royal Society
Stable URL: http://www.jstor.org/stable/40538242 .
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PHILOSOPHICAL
TRANSACTIONS
of
*T%
R.
Phil.Trans. Soc. B (2010) 365,765-773
doi:10.1098/rstb.2009.0240
THE ROYAL
W’
SOCIETY JLß
Review
Peroxisome diversity and evolution
Toni Gabaldón*
88
Centre Genomic
(CRG), Dr Aiguader, 08003 Barcelona,Spain
Regulation
for
of
in
that
membrane can be found all major
bounded a single
are
Peroxisomes organdíes
groups
by
in
is supported thepresence,
cellular
A
by
compartment
evolutionary ofthis
origin
eukaryotes.single
and
in
set
of
diverse
biogenesis maintenance.
implicated peroxisome
organisms, a common ofproteins
of
a
level evolacross
can
Their
however, vary
indicatinghigh
content,
substantially species,
enzymatic
in
on
ourknowledge peroxisomes some
havegreatly
Proteomic
expanded
analyses
utionary
plasticity.
we
havea limited
and
mammals yeasts.
modelorganisms,
However, still
knowledge
including
plants,
of
of
in
ofperoxisomes thevastmajority groups microbial
and
aboutthedistribution functionalities
and
of
recentadvancesin our understanding peroxisome
diversity
Here, I review
eukaryotes.
in
on
with
eukaryotes.
evolution, a special
emphasis peroxisomes microbial
evolution;
proteome
glycosomes;
glyoxysomes;
Keywords:peroxisomes;
This
of
in
narrow
1. INTRODUCTION
range species.
onlybe found a very
in
luciferase fireflies
were
named microbodies, first is the case forthe fluorescent
Peroxisomes,
initially
for
on
notedbyRhodin(1954) as partofhis PhD thesis
(Gould et al. 1987) or forseveralkeyenzymes
to
are
which restricted a
of
mouse theproduction penicillin,
tubulecellsfrom
of
themorphology proximal
few fungalgenera such as Pénicillium
as
theirinitialcharacterization a
(Kiel et al.
However,
kidney.
in contrast,
novel type of cellularorganellecame years later, 2000). Other peroxisomal
pathways,
such
distribution as theß oxiableto iso- showa more
de
when
Christian Duve andhisteamwere
widespread
of
acidsor thesetofenzymes
from rat liver and study their dation fatty
late peroxisomes
responsible
such
stress
biochemical
Despitedisplaying
response.
(de
properties Duve & Baudhuin1966). foroxidative
all
the
de Duve’s groupidentified presenceof several high levels of metabolicdiversity, peroxisomes
in
involved
set
a
and
in
involved theproduction degradation havein common similar ofproteins
enzymes
as
and
andhencegavethenameperoxi- their
ofhydrogen
biogenesis maintenance, wellas theuse
peroxide
the
for
Since then,peroxisomes ofsimilar
somesto theseorganelles.
signals directing localization
targeting
of
The presence these
to
of
from variety other
a
havebeen isolated
organisms of proteins the organelle.
evolutionthe
traits
metabolic common
that
anditsoonbecameevident thespecific
supports idea ofa single
the exact
from ary originfor all peroxisomes,
can
of
although
substantially
properties peroxisomes differ
scenario still remains somewhat controversial
at thelevelofa single
Even
to
organspecies species.
can
enzymatic (de Duve 2007).
ism, peroxisomes displayalternative
several
breakwe
In recent
contents
years, havewitnessed
dependingon the specifictissue or the
considered.
conditions
environmental
Indeed, some throughsin peroxisomeresearch,includingthe
in
involved
mechanisms
of
or elucidation themolecular
of
in
found specific
groups organisms
peroxisomes
as
of
and
classi- theformation division peroxisomes wellas
wereinitially
that
are
tissues so divergent they
of
fied as distinct organelles and are still now the finding novelclues about their
possibleevolnames. For utionary
to
referred with alternative
origin(van der Zand et al. 2006). While
commonly
our
advanced understanding
have
in
specieshar- suchfindings clearly
instance,
peroxisomes trypanosomatid
of
and evolution these widespread
of the function
and are therefore
reactions
bour certainglycolytic
thereis stilllittleinformation
as
known glycosomes
regarding
(Michelset al. 2006), whereas organelles,
across
of
and
are named glyoxysomes the distribution diversity peroxisomes
some plant peroxisomes
oftheglyoxylate the major groupsof eukaryotic
harbour
Indeed,
becausethey
organisms.
enzymes
mainly
comes
about peroxisomes
a
et
fungi, par- most of our knowledge
(Hayashi al. 2000). In filamentous
cycle
in
of
the
to
referred as theWoronin from characterization peroxisomal
of
ticular
proteins
type peroxisome,
the
of
of
in
functions themaintenance cellular
integrity a handful model species,including human,
body,
Pichia
to
cerevisiae,
by sealingthe septalpore in response wounding rat,mouse, the yeastsSaccharomyces
and Yarrowia
Hansenulapolymorpha
can pastoris,
et
lipolytica,
enzymes
(Würtz al. 2009). Some peroxisomal
thaliana.These
and the model plant Arabidopsis
two
model organisms
onlypartially of the
represent
is
in
five
es
diversity cureukaryotic
majorgroups which
*tgabaldon(^crg.
classified
1)
(Keelinget al. 2005) (figure and,
rently
of
of
One contribution 12 to a ThemeIssue ‘Evolution organellar
of
withthe notableexception yeast,theyrepresent
in
metabolism unicellular
eukaryotes’.
765
is
Thisjournal ( 2010 The Royal
Society
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All use subject to JSTOR Terms and Conditions
766 T. Gabaldón Review.Peroxisome
and
diversity evolution
across the eukaryotic
treeof lifeis represented.
The level of inforFigure 1. Our stateof knowledgeon peroxisomediversity
mationofperoxisomes based on literature
is
searchesforeach taxa and theirmajorrepresentatives.
Circlesnextto thedifferent
taxa indicatethe typeof information is availableon peroxisomes.Red circlesindicatesthatforthisgroup,extensive
that
biochemical data as well as comprehensive
proteomicsand bioinformatics
surveysare available. Orange circles indicate an
intermediate
level of information peroxisomalcomposition,mostlybased on biochemical studies of individualproteins
on
or pathways
coupled withcomprehensive
sequence analysesto predictperoxisomallocalization.Yellow circlesindicatethat
the presenceof peroxisomesin thatgroup is well establishedbut thatthe level of the characterization theirfunction
of
and
withinthis group is veryscarce. White circlesindicate that the presence of peroxisomeshas been studied in this
diversity
an
group revealing apparentabsence of these organdíes in all the membersstudied (only a white circle is associated with
the group) or in some of them (circleswithdifferent
colours are associated withthe group). Absence of a circlenextto the
contentin this group remainsto be clearly
group indicatesthatthe presenceor absence of peroxisomesor theirenzymatic
established.(Adapted froma modified
versionof fig. 1 of Keeling et al (2005).)
the
complex multicellular
organisms.Only recently,
interest has partially shifted to peroxisomes in
microbialeukaryotes.
Consideringtheiradaptationto
a variety niches and life styles,it is among these
of
in
organisms,where the highest diversity terms of
metabolic properties of peroxisomes is expected.
Thanks to the availability completelysequenced
of
genomes for a growingnumber of microbial eukarto
yotes,we are now just starting unveil the existing
of
diversity peroxisomesin these organisms.
In thisreview, willprovidean overview the curI
of
rent state of our knowledgeon peroxisomediversity
and evolution. For this, I will firstfocus on the
common mechanisms shared by all peroxisomesto
then survey
what is knownto be specificin the major
of eukaryotictaxa. When discussing this
groupings
metabolic diversity,
and to provide a logical framework, I will follow the classificationof eukaryotic
taxa intofive
majorgroups,namelyUnikonts,
Plantae,
and Rhizaria,as described
Excavates,Chromalveolates
Phil. Trans. Soc. B (2010)
R.
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Review.Peroxisome
and
diversity evolution T. Gabaldón 767
The
2.
view
and
which
the
(full-line
boxes),
Figure A schematic oftheperoxisome. biogenesis maintenance
processes
comprise
in
in
involved protein
and
are
of
The
content the
of
division, present alltypes peroxisomes. enzymatic
import organelle
proteins
with
different
sets
in
variable,
(dashed-line
boxes)is highly
enzymatic beingpresent different
peroxisome
species.
Enzymes
involved fatty metabolism reactive
in
acid
and
are
Other
additional
(in
oxygen
speciesdetoxification widespread.
pathways
be
to
of
The
at
side
someimportant
blue)might restricted certain
groups eukaryotes. text theright-hand ofthefigure
provides
aboutthediversity evolution eachdepicted
and
of
remarks
process.
by Keeling et al. (2005). Finally,I will discuss our
of
understanding how the peroxisomalproteomehas
been shaped duringevolutionand the current
debates
on the possible evolutionary
of this intriguing
origin
organelle.Throughoutthe text,an emphasis will be
put on microbialeukaryotes.
2. DIVERSE BUT ALL THE SAME: COMMON
TRAITS OF PEROXISOMES
A general
of
that
description peroxisomes would fit
mostorganisms be thatof a singlemembranewill
withfairly
conserved
for
boundedorganelle
systems
and maintenance witha highly
but
their
biogenesis
content
variable
2).
enzymatic
(figure The peroxisoinvolved fatty
in
mal lumenoften
harbours
enzymes
of
and the detoxification reactive
acid metabolism
In
a
of
anaoxygen
species. addition, multitude other
in
havebeen observed
bolic and catabolic
processes
or
certain
taxa. In contrast mitochondria chloroto
do
plasts,peroxisomes not possess an organellar
All peroxisomalproteins are therefore
genome.
in
and
encoded thenuclear
by
genome translated cytosolic ribosomes.These proteinsmust then be
into
by
import
incorporated the organelle specific
of
which on thepresence targeting
routes,
signals
rely
in their
sequences(Brown& Baker2008; Girzalsky
of
etal. 2009; Ma & Subramani
2009). The majority
use
matrix
proteins a short
peroxisomal
peroxisomal
which
signal (PTS) at theirC-terminus,
targeting
aminoacidsSKL or conof
consists thethree
mainly
residues
situated
variants
servative
thereof,
although
on
seemto havean influence thetransport
upstream
&
however,
(Brocard Hartig2006). Otherproteins,
use thealternative
PTS2 with conthe
bi-partite
signal
sensussequence [RK]-[LVI]-x5-[HQ]-[LA]at their
In
N-terminal
someperoxisomal
region. addition,
proteins notpossessa recognizable
do
and
targeting
signal
aretransported peroxisomes
into
associated
with
other
domains Pex5 or with
of
other
PTS-carrying
proteins
(van der Klei & Veenhuis
2006a). Targeting
signals
are recognized a molecular
that
by
machinery carries
This
into
matrix.
peroxisomal
proteins theorganellar
to
import complex,referred as the importomer
of
(Agneet al. 2003), consists two mainfunctional/
structural
modules: a membrane
proteincomplex
the
Pexl3 and
including receptor
dockingproteins
Pexl4 and a receptor
module on the cytoexport
plasmic side containing several RING-domain
proteins,ubiquitinating
enzymes and the AAAATPases Pexl and Pex6 (Grou et al. 2009). This
is
suchas Pex5 and
system used byreceptor
proteins
in
Pex7, whichshuttle and out of the peroxisome,
their
thereby
cargoesintotheperoxisomal
importing
machinmatrix.
the
import
Importantly, peroxisomal
has no resemblance thoseof otherorgandíes
to
ery
and
such as mitochondria chloroplasts, presents
and
able
folded
the
of
proteins
particularity
being totransport
et
(McNew &
(Walton al. 1995) and evenoligomers
of
Goodman1994). Despitethepresence a common
in
involved theimport peroxisomal
of
set ofproteins
in
this system
particularities
proteins,
may present
For instance,
the
the different
taxonomic
groups.
a
5.
possesses setofbiogenesis
proteins
yeast cerevisiae
beenfound
in
ofwhich
for13 havenotyet
homologues
et
(Schlüter al. 2006), although
plantsor mammals
amongfungi(Kiel et al. 2006).
theyare conserved
thatseemsto be sharedby all
Another
mechanism
Phil Trans. Soc. B (2010)
R.
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768 T. Gabaldón Review,
Peroxisome
and
diversity evolution
3.
view
shows
Figure A schematic ofmammalian
(a)
cell,
peroxisomes. Micrograph
partofa ratliver where
(P),
peroxisomes
can be seensurrounded other
cellular
such
reticulum and
by
compartments as thenucleus
(N), therough
(ER)
endoplasmic
mitochondria
lattice
formed
insideperoxisomes,
whichresults
from
bound enzymatic
(M). Note the crystalline
tightly
material.
Picture
of
ofthe
kindly
provided DouglasF. Bray
by
(University Lethbridge). A reconstruction peroxisomal
(¿>)
proteome metabolism inferred proteomics is shown.
and
as
from
data
Colourcodesindicate likely
the
of
evolutionary
origins the
as
and
proteins follows:
red,
green,
alphaproteobacterial;
blue,
yellow,
eukaryotic; actinomycetales; cyanobacterial; white,
undetermined.
from modified
a
version fig.5 ofGabaldónetal. (2006).)
of
(Adapted
is
for
typesofperoxisomes thatresponsible thedivision
of the organelle.In recentyears,therehas been a significant
in
progress the elucidationof thismechanism,
whichhas been shownto be largely
conservedin yeast,
and mammalian peroxisomes. This division
plant
machineryinvolves,at least, a dynamin-like
protein
and a TPR (Tetratrico tide Repeat)-motif
containPep
ing protein that serves as a membrane anchor.
these proteinsare also involvedin mitoInterestingly,
chondrial fission,establishinga link between these
organdíes (Delille et al. 2009).
In terms metabolism, picture rather
of
the
is
different
and extremely levelsofdiversity be foundacross
can
high
different
taxa. Althoughmost peroxisomesshare the
presence of some fattyacid oxidation routes, etherand
for
of
lipidbiosynthesis enzymes the detoxification
reactive
oxygenspecies,thereseems to be no common
set of enzymes
thatcorrelates
withtheprescompletely
ence of peroxisomes,
that is, enzymespresentin all
species with peroxisomesbut absent fromorganisms
devoidoftheorganelle(T. Gabaldón & B. Gasse 2009,
unpublisheddata). This view of the peroxisomeas an
withfairly
conserved
organelle
biogenesisand maintenance mechanisms witha largely
but
variableenzymatic
contentshaped to the specific
needs of each organism
or tissueis likely become moreestablished peroxito
as
somes fromnovel organismsare characterized. the
In
I
overview the
of
sections, willprovidea brief
following
main metabolic characteristics peroxisomesfrom
of
themajoreukaryotic
groups.
3. PEROXISOMES IN UNIKONTS
Unikonts constitutea recentlyproposed taxonomic
group that includes amoebozoans, metazoans and
fungi (Cavalier-Smith 2002). Without any doubt,
thisgroup is the one forwhichwe knowmore details
about its peroxisomes. Peroxisomes of metazoans
such as human, mouse or rat have been extensively
characterized
(Schlüteretal. 2007). For instance,
proteomicanalysesof ratliverperoxisomeshave reported
more than 50 peroxisomal proteins (Kikuchi et al.
2004; Islingeret al. 2006). A wide rangeof enzymatic
functions
have been identified mammalianperoxiin
somes includinga oxidation of branched chain fatty
acids, amino acid metabolismand different
steps for
the synthesisof purines, pyrimidines,cholesterol,
etherlipids and bile acids (figure3). Comparisonsof
tissues such as mouse
peroxisomes from different
liverand kidney(Mi et al. 2007) have pointed to the
existenceof tissue-specific
specializations.
Severalmicrobialeukaryotes
belong to the Unikont
unicellularfungiand amoebozoans
group, including
such as the slime mould Dictyostelium
discoideum,
whereperoxisomes
have been identified microscopy
by
and biochemicalassays (Parish 1975). However,information regarding the enzymatic content of
amoebozoan peroxisomes is very scarce. Different
studies on D. discoideum
peroxisomeshave identified
citrate synthase, catalase, the multi-functional
acid ß oxidation and the purine
enzyme of the fatty
metabolism enzymes phosphodiesterase and urate
oxidase (Hayashi & Suga 1978).
In contrastto amoebozoan peroxisomes,those of
havebeen intensively
studied.Indeed,peroxisome
fungi
research takengreatadvantageofthewealthofmolhas
eculartools and genomicresources themodel yeast
for
5. cerevisiae.For instance, several comprehensive
studies including the analysis of gene expression
induced by growth in oleate (Smith et al. 2002),
large-scale fluorescencemicroscopyof GFP (Green
FluorescentProtein)-fused
proteins(Huh et al. 2003)
Phil. Trans. Soc. B (2010)
R.
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Review.
Peroxisome
and
T.
diversity evolution Gabaldón 769
4.
cerevisiae
and
as inferred proteomics Colour
from
data.
codes in
as
Figure Saccharomyces peroxisomal
proteome metabolism
3.
from
version fig. ofGabaldón al. (2006).)
of 5
et
figure (Adapted a modified
or subcellular
of
have
proteomics highly
pureperoxisomal as in other
eukaryotic
groups,
peroxisomes been
fractions
et al. 2001; Yi et al. 2002) are lostfrom
somefungal
suchas thosebelonging
(Schafer
species
the
of
approaching fullcharacterization the protein to theMicrosporidia.
of
in
repertoirethis
organelle.
Enzymes
present theperoxisomes S. cerevisiae mainly
of
are
in
involved fatty
acid
aminoacid metabolism thedetoxifica- 4. PEROXISOMES IN PLANTAE
and
oxidation,
tion of reactive
of
Plantae characterized the
are
oxygen
species derivedfromthese Members thegroup
by
reactions
of
derived primary
4).
(figure Otheryeastspeciesmaydisplay presence plastids
by
endosymbiosis.
in
metabolic
this
quitea different
repertoire their
peroxi- Besideshigher
plants(Viridiplantae), groupalso
in
thesebeingspecialized the metabolisms
of includes
microbial
such
somes,
photosynthetic
eukaryotes as
unusualcarbonand organic
several
sources glaucophytes,
and redalgae.Peroxisomes
nitrogen
green
algae
usedfor
studied higher
in
where
(van
20066).For havebeen extensively
growth derKlei & Veenhuis
plants,
boi- they
rolesin many
instance,
methylotrophic species Candida
yeast
(e.g
playimportant
processes
including
H.
P
induceperoxisome seed germination, senescence,
leaf
fruit
diniiy polymorpha, pastoris)
maturation,
on
as
to
development
during
growth methanol a sole response abioticand bioticstress,
photomorphocarbonsource.These peroxisomes
harbour
enzymes genesis, photorespiration,
biosynthesisof plant
for
metabolism as alcohol
such
oxi- hormones cell signalling reactive
and
and
necessary methanol
by
oxygen
dase and dihydroxyacetone
which may nitrogen
not
as
synthase,
species.Although as extensively in
account up to 70 per centof theprotein
for
content mammals yeasts,
and
studies
havebeenperproteomic
in the cell. In filamentous
formed plantperoxisomes
on
et
fungi,
peroxisomes
may
(Reumann al. 2007;
in
alsobe involved a number biosynthetic For Eubel etal. 2008; Palmaetal. 2009). These,together
of
roles.
are
instance,
peroxisomes theplace forthefinal
steps with computational
analysesof proteinsequences
of the synthesis the antibioticpenicillinin (Reumannet al. 2004), have helped to identify
of
a
P chrysogenum der Klei & Veenhuis20066). widevariety biochemical
of
in
(van
pathways
present perOtherfilamentous
crassa oxisomes. Among many other pathways,plant
fungisuch as Neurospora
induce a special type of peroxisome,
have been shownto containenzymes
glyoxysomes, peroxisomes
on
in
involved thepentose
oxidation
duringgrowth ethanolor acetate (Kionka &
phosphate
pathway,
in
Kunau 1985). Similar glyoxisomes plants,
to
these of fatty
acids, ascorbate-glutathione
cycle,biosynare characterized theirenrichment
in thesisof jasmonicacid and auxin, metabolism
of
organdíes
by
fromthe glyoxylate
oxideand reactive
Plantperoxicycle such as malate nitric
enzymes
oxygen
species.
and isocitrate
of
and
Moreover,
synthase.
synthase
peroxi- somesshowa highdegree tissuespecialization
lack the enzyme
catalase.Finally, at leastfour
somesin N. crassa
distinct
of
havebeen
types thisorganelle
Phil. Trans. Soc. B (2010)
R.
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770
T. Gabaldón Review.Peroxisome
and
diversity evolution
described.
Undifferentiated peroxisomes
contain groups(e.g. apicomplexans ciliates).Thanksto
and
plant
catalase uricase.
and
are
of
mainly
Glyoxysomes enriched the availability severalgenomicsequencesfrom
with
of
acid
and
we
to
enzymes thefatty oxidation theglyox- thiseukaryotic
group, are now starting havea
and theircombined
actionallowsthese glimpse thediversity peroxisomal
of
of
of
metabolism
ylatecycle,
to convert
the seed storagelipids into these
Forinstance, silico
in
ofbiogenorgandíes
species.
analyses
for
and
sugar,
necessary seedgermination subsequent esis markershave identified
apicomplexans
(e.g.
Leaf peroxisomes,
in
as
which
lacks
growth.
present photosynthetic Plasmodium) thefirst
eukaryotic
group
are
in
of
in
of
mitochondria
tissues, specialized themetabolism glycolate peroxisomes thepresence classical
and host many of the enzymes necessaryfor (Schlüter al. 2006). Otherchromalveolates as
et
such
another
of
of
and
photorespiration.
Finally,
type peroxisomes theciliates thegeneraTetrahymena Paramecium
in
hasbeenidentified theroot
nodules certain
of
et
tropi- do possessthisorganelle
(Müller 1973; Stelly al.
in
cal legumes, whichthe synthesis allantoin
of
is
have
1975). In oomycetes,
peroxisomes beendetected
carried
out.
in the genusPhytophthora
et
(Philippi al. 1975) and
In contrast therelatively amount infor- havebeenpredicted be present thediatomThato
of
to
in
large
mationavailablefor higherplants,littleis known lassiosira pseudonana (Armbrust et al. 2004).
aboutthediversity functions peroxisomes uni- However, presence peroxisomes other
of
of
in
the
of
in
chrocellular
The presence peroxisomes been malveolatesremainsto be established.Genomic
of
has
plants.
in
searchesfor core peroxisomal
in
reported several
greenand red algae (Codd et al.
proteins available
et
their
do
a
distribution peroxiof
1972; Shinozaki al. 2009). However,
specific sequences suggest patchy
metabolic
remains
to
repertoire
largely be described. somes in severalof these groups(T. Gabaldón &
B. Gasse 2009, unpublished
data).
5. PEROXISOMES IN EXCAVATES
Excavates the majorassemblage protists.
are
of
The
7. PEROXISOMES IN RHIZARIA
includes broad
a
of
is
for
group
diversityfree-living,
symbiotic Rhizaria theonlymajoreukaryotic
supergroup
orparasitic
which
often classical
lack
mitochon- whichno complete
has yetbeen
forms,
genomesequence
dria(see paperby Embley al. 2010). Some of the obtained. is as wellone ofthemostrecently
et
It
created
from group,
this
suchas theparasitic
and
species
protozoan groupings,
Cercozoa, foraminifera
comprising
Giardia
are
also
lamblia^ apparently devoidof peroxi- radiolarians
(Cavalier-Smith
2002). Studiesreferring
somes (de Souza et al. 2004). Otherssuch as the toperoxisomesrhizarians very
in
are
scarce.
Peroxisomes
do
derivedtype of havebeendescribed solitary
as
in
forkinetoplastids possess a highly
organelles several
referred as glycosomes
to
&
aminiferan
thosethatinhabit
the
peroxisome
(Opperdoes
species,including
Borst1977). This groupof flagellate
com- chemocline marine
of
sediments
&
protozoa
(Bernhard Bowser
human pathogenssuch as the 2008). In such anoxic environments,
Foraminifera
prises important
of
and species mightbe associatedwithsulphur-oxidizing
trypanosomatids the genera Trypanosoma
which
haverecently
received
considerable microbial
where
micromolar
levelsofH2O2 are
Leishmania^
mats,
attention. peroxisomes theseorganisms
The
of
have observed.
of
foraminiInterestingly,
peroxisomes these
theparticularitygenerally
of
catalaseand har- feraspecieshavebeen proposed participate the
to
in
lacking
a
of
In
down of environmental
bouring number glycolytic
enzymes. addition, breaking
hydrogen
peroxide
theseorgandíes
additional
from to produce oxygen,
whichwould be subsequently
maycontain
enzymes
a variety processes
of
such as ß oxidation fatty used in aerobic pathways(Bernhard& Bowser
of
the
sal- 2008). Such a model…
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