Species of single-celled organism
Chilodonella uncinata
is a
single-celled
organism of the
ciliate
class of
alveoles
. As a
ciliate
,
C. uncinata
has
cilia
covering its body and a dual nuclear structure, the
micronucleus
and
macronucleus
.
[2]
[3]
[4]
[5]
Unlike some other ciliates,
C. uncinata
contains millions of
minichromosomes
(
somatic chromosomes
) in its macronucleus while its micronucleus is estimated to contain 3
chromosomes
.
Childonella uncinata
is the causative agent of
Chilodonelloza
, a disease that affects the gills and skin of fresh water fish, and may act as a
facultative
of mosquito larva.
Habitat
[
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]
Chilodonella uncinata
has a cosmopolitan distribution. It is suspected to act as a
facultative
endoparasite
of the larvae of the
Culex
,
Aedes
, and
Anopheles
mosquito larva. It lives in fresh water ponds, lakes, creeks, and bayous where it feeds on bacteria and other microbes.
Microscopic examination of cytological samples showed that mosquito larva containing subcutaneous encysted
C. uncinata
had a 25-100% mortality in the mosquito larva, but no viability examinations were conducted.
[6]
Biology and morphology
[
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]
Chilodonella uncinata
has a broad
thigmotactic zone
that is two-thirds the length of the body width and has a pronounced anterior beak that is directed to the left.
[7]
It can be maintained under laboratory conditions in a cereal wheat grass media inoculated with
Klebsiella
sp
. Optimal growth occurs between 25 and 30 °C.
C. uncinata
is capable of
sporulation
and can resist environments with limited resources for a period of time.
Genome structure
[
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]
All
ciliates
have two
nuclei
, but they differ in their structure of the somatic nucleus. All
ciliates
except
Karyorelictea
have a dividing macronucleus.
[8]
C. uncinata
also has a dividing macronucleus, but it modifies its macronuclear genome from the maternal micronuclear genome by producing macronuclear chromosomes that contain one or two
open reading frame
(ORFs). The average size of these macronuclear chromosomes is 4 kbit/s.
[4]
The macronuclear chromosomes are also amplified to produce a high variable copy number between the chromosomes. For example, chromosome A may have 500 copies while chromosome B only has 5 copies in the macronucleus. This leaves the macronuclear genome with millions of individual chromosomes, all containing
telomere
ends, only one ORF, and little area for transcription factor binding for initiation of transcription.
Internally eliminated sequences
[
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]
Internally eliminated sequences
(IES) are noncoding regions of the
germ-line
genome found in
Ciliates
. They are defined as sections of DNA removed from the diploid micronuclear genome during which a copy of the micronuclear genome is converted to the macronuclear genome even though errors occur in which an IES sequence may not be deleted.
[2]
There is little conservation of motifs between Ciliate species; however,
C. uncinata
, like other ciliate species, show a conserved IES sequence motif within a species.
[9]
It is unknown if IES sequences have a function in the genome, but in the ciliate
Paramecium
, an IES sequence is used to determine the mating type of an individual. When a specific IES sequence is not deleted from the developing somatic nucleus, then it is type O mating type. However, if that IES is deleted from the developing macronucleus, it is type E mating type.
Paramecium
can only mate with individual of opposite mating type.
Unlike
Tetrahymena
or
Paramecium
, it has been observed that
C. uncinata
has a larger number of IES sequences within a single protein-coding gene than in other ciliates . Also there exists populations of
C. uncinata
that contain an IES sequence that other populations do not carry.
Reproduction and division
[
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]
Chilodonella uncinata
has sexual conjugation for
recombination
, and replication of the cell occurs by asexual division
[4]
Sexual conjugation
[
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]
Sex and reproduction are separate in ciliates.
[10]
C. uncinata
is capable of mating with other
C. uncinata
cells that have the same
mating type
. After
mating type
complementary, the germ-line nucleus undergoes meiosis to produce
zygotic
nuclei. Each conjugated cell transfers one zygotic nucleus to the other cell where the zygotic nuclei fuse. The diploid germ-line nucleus undergoes mitosis which creates a duplicated germ-line nucleus. At this point the somatic nucleus is being degraded.
The duplicated germ-line nucleus then develops into the new somatic nucleus. The genomic structure of the somatic nucleus is being created by chromosomal fragmentation with single-gene chromosomes and amplification of these somatic chromosomes. It is unknown what determines the copy number of each chromosome or if the copy number of the somatic chromosomes are heritable between sexual conjugations.
Asexual reproduction
[
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]
C. uncinata
goes through asexual reproduction for cell division and duplication called
amitosis
. As
C. uncinata
has two nuclei, it goes through two different styles of division of the nuclei. The germ-line nucleus goes through
mitosis
during asexual division while the somatic nucleus undergoes
amitosis
. Amitosis is a stochastic process where unlike in mitosis, there is no spindle formation to segregate chromosomes during nuclear division. Instead, the chromosomes within the somatic nucleus are duplicated, and the nucleus goes through binary division. The precise mechanism is unknown, but it is believed that somatic chromosomes that are located on one side of the dividing somatic nucleus are distributed to one daughter cell, and the somatic chromosomes on the other side of the nucleus are distributed to the other daughter cell.
This amitotic process causes the two daughter cells to potentially have identical germ-line nucleus but a different somatic nucleus in regards to the copy numbers of the chromosomes. As the somatic nucleus is the nucleus that is transcriptionally active, this somatic copy number mutation derived by the amitotic process could have fitness consequences for the individual cell.
Use in genomic research
[
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]
Childonella uncinata
is easily cultured in the laboratory, has a fast generation time, and has a complex genomic structure that allows
C. uncinata
to be a
model organism
for
genomic architecture
,
genomic networks
, and
genome evolution
research.
[11]
Specifically,
C. uncinata
along with other closely related
Ciliates
has been used to determine the evolution of duplication of the
alpha-tubulin
gene. It was found that
C. uncinata
contains two paralogs of
alpha-tubulin
where the variation between the
paralogs
is highly concentrated within three small areas of the gene.
[12]
References
[
edit
]
- ^
Alan Warren (2010).
"
Chilodonella uncinata
(Ehrenberg, 1838)"
.
WoRMS
.
World Register of Marine Species
. Retrieved
January 20,
2012
.
- ^
a
b
Zufall, Rebecca A.; Katz, Laura A. (2007). "Micronuclear and Macronuclear Forms of ?-Tubulin Genes in the Ciliate Chilodonella uncinata Reveal Insights into Genome Processing and Protein Evolution".
The Journal of Eukaryotic Microbiology
.
54
(3): 275?82.
doi
:
10.1111/j.1550-7408.2007.00267.x
.
PMID
17552983
.
S2CID
15586012
.
- ^
McGrath, C. L.; Zufall, R. A.; Katz, L. A. (2006). "Ciliate genome evolution". In Katz, Laura A.; Bhattacharya, Debashish (eds.).
Genomics and Evolution of Microbial Eukaryotes
. Oxford University Press. pp. 64?77.
ISBN
978-0-19-922905-5
.
- ^
a
b
c
Prescott, DM (1994).
"The DNA of ciliated protozoa"
.
Microbiological Reviews
.
58
(2): 233?67.
doi
:
10.1128/MMBR.58.2.233-267.1994
.
PMC
372963
.
PMID
8078435
.
- ^
Yao, Meng-Chao; Duharcourt, Sandra; Chalker, Douglas L. (2002).
"Genome-Wide Rearrangements of DNA in Ciliates"
. In Craig, Nancy L. (ed.).
Mobile DNA II
. pp. 730?758.
ISBN
978-1-55581-209-6
.
- ^
Bina Pani Das (2003).
"Chilodonella uncinata ? a protozoa pathogenic to mosquito larvae"
(PDF)
.
Current Science
.
85
(4): 483?489
. Retrieved
17 February
2011
.
- ^
Lynn, Denis H. (2008).
The Ciliated Protozoa: Characterization, Classification, and Guide to the Literature
. Berlin: Springer. p. 183.
ISBN
978-1-4020-8238-2
.
- ^
Katz, LA (2001).
"Evolution of nuclear dualism in ciliates: a reanalysis in light of recent molecular data"
.
International Journal of Systematic and Evolutionary Microbiology
.
51
(Pt 4): 1587?92.
doi
:
10.1099/00207713-51-4-1587
.
PMID
11491362
.
- ^
Chalker, Douglas L.; La Terza, Antonietta; Wilson, Allison; Kroenke, Christopher D.; Yao, Meng-Chao (1999).
"Flanking regulatory sequences of the Tetrahymena R deletion element determine the boundaries of DNA rearrangement"
.
Molecular and Cellular Biology
.
19
(8): 5631?41.
doi
:
10.1128/mcb.19.8.5631
.
PMC
84415
.
PMID
10409752
.
- ^
T. Robinson & L. A. Katz (2007).
"Non-Mendelian inheritance of paralogs of 2 cytoskeletal genes in the ciliate
Chilodonella uncinata
"
.
Molecular Biology and Evolution
.
24
(11): 2495?2503.
doi
:
10.1093/molbev/msm203
.
PMID
17890762
.
- ^
Spring, KS; Pham, S; Zufall, RA (2013).
"Chromosome copy number variation and control in the ciliate Chilodonella uncinata"
.
PLOS ONE
.
8
(2): e56413.
Bibcode
:
2013PLoSO...856413S
.
doi
:
10.1371/journal.pone.0056413
.
PMC
3577910
.
PMID
23437129
.
- ^
Israel, RL; Kosakovsky Pond, SL; Muse, SV; Katz, LA (2002). "Evolution of duplicated alpha-tubulin genes in ciliates".
Evolution; International Journal of Organic Evolution
.
56
(6): 1110?22.
doi
:
10.1554/0014-3820(2002)056[1110:eodatg]2.0.co;2
.
PMID
12144013
.
External links
[
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]