Identification of Cyanophage Ma-LBP and Infection of the Cyanobacterium M. aeruginosa from an Australian Subtropical Lake by the Virus ( Stephen & Peter, 2004)

Prof.: Dr. Hul SeinghengSubject :General Microbiology Group 2 : DYSI Nora EK Pichmony Hak Rany HE Ravy Horn chanrithy

Academic year 2010-2011

Institute of Technology of Cambodia

Department of Chemical and food technology

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Key termsCyanophage :

◦phage that infects to cyanobacteria◦Virus specific to cyanobacteria

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• Infection:

• Lysis: dissolution or destruction of cells, such as blood cells or bacteria, as by the action of a specific lysin that disrupts the cell membrane.

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Why was this research conducted?

Toxic cyanobacteria are common seasonal inhabitants of subtropical lakes in Queenland, Australia. ( late autumn and early spring)

It could be because of :Natural control by cyanophage

Environmental factors : influence the ability of virus to infect, lyse the host.

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Objectives of researchto determine whether

Cyanophage influence on the abundance of M. aeruginosa blooms.

Identify the Cyanophage Ma-LBP.

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Material and MethodsMaterialsSampling site : Lake Baroon,

South EastQueenland, Australia

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Materials

Field sample : - collected in March, April, June and July 2001

- from intake tower , north and south swimming pool( at the surface, at 3, 6 and 9m depths)

Water samples mixed before further subsampling

Host growth medium : B-12 medium for isolated and grow M.aeroginosa.

Material and Methods

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Methods

Material and Methods (con’t)Isolating M.aeroginosa from Lake Baroon• Calculate the growth and replication

Collecting viruses from Lake Baroon• Collect the virus from supernatant M.aeroginosa growth and generation time assays Determining viral numbers

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Stained cyanophage used to assess infectionCyanophage replication rate and lysis assay• Add the natural viral population to the

cultured host population ( 6 days)Determining cyanophage burst size• Quantified the cyanophage releasedIsolation of M.aeruginosa phage for TEMData analysis

Material and Methods (con’t)

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ResultsM.aeruginosa growth rate

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Lysis assaysResults

The more VLPs that were present at the start of the incubation, the more and faster the host population decreased.

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ResultsObserving viral infection and lysis

A. Cell wall rupture

B. Cytoplasm leakage

C. Whole cells

Viral burst size : -28 cyanophage per cell

-each cycle of replication cycle 11.2h

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TEM studied to characterize the cyanophage

Results

T7-like morphology with short geometries tail : family Podoviridae

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DiscussionImportant finding: the quantitive

demonstration of cyanophage that are infective for M.aeruginosa

TEM of Cyanophage Ma-LBP is same as TEM picture of Podoviridae

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DiscussionInfection, lysis and immunity

◦Host decrease 95% within 6 days when Cyanophage Ma-LBP in original sample=0.23% from the sampling

No bloom can form , if nothing interfere with the Cyanophage ability

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DiscussionHowever….. After the lysis assays

◦host cells (after 95% reduction). Then we add Cyanophage again.

◦ This acclimated host cells attained natural population densities in 3 weeks with a resistance to the Cyanophage Ma-LBP.

The host may have simply become resistant

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ConclusionControl of bloom formation

◦Cyanophage presence possibly suppressed M.aeruginosa abundance.

◦Cyanobaterial blooms may results from condition in the lake that both favor host growth and prevent viral infection and lysis.

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RecommendationResearch aims

◦to understand physical and chemical factors that might control toxic cyanobaterial blooms

consider the factors might interfere with the binding, infection, and lysis of the host’s cyanophage.

Should also..

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Reference Tucker, S. & Pollard, P. (2005).Applied and

Environmental Microbiology: Identification of Cyanophage Ma-LBP and Infection of the Cyanobacterium Microcystis aeruginosa from

an Australian Subtropical Lake by the Virus.71:2. pp 629-635. Doi: 10.1128/AEM.71.2.629-635.2005

Thank you for attention!

Welcome for questions and comments!