Phycology جلبک شناسی

نخستین پایگاه اطلاعاتی جلبک شناسی به زبان فارسی

نرم افزار شمارشگر جلبکها Algae counting software

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لطفا به مطلب اصلی در بخش ادامه مطلب مراجعه فرمایید.

 

ادامه مطلب   
نویسنده : رضا رمضان نژاد قادی/ آرش کیانیان مومنی ; ساعت ۱۱:٠٦ ‎ق.ظ روز پنجشنبه ۱٥ بهمن ۱۳۸۸
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رفع آلودگی یوکاریوتی از محیط کشت سیانوباکترها

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در ادامه مطالب پیشین، برای رفع آلودگی یوکاریوتها از محیط کشت سیانوباکترها روشهای زیر پیشنهاد میگردد. مورد نخست از پروفسور ویتون از انگلستان و مورد بعد از پروفسور حمید از پاکستان ارسال شده است.

 

Dear Reza

Getting rid of eukaryotes from cyanobacterial cultures should be simple and routine with cycloheximide.  I've done it since the time cycloheximide was sold as actidione (almost forty years ago!).  The only problems have been the occasional resistant testate amoeba or ciliate.  

   Obtaining bacteria-free cultures is of course much more of a challenge, especially those where bacteria are routinely attached to the surface, such as the heterocysts of many Cylindrospermum species.   For bacteria it is often best to work with single filaments, preferably hormogonia.  In the case of filamentous forms, the majority of species form hormogonia when a period of moderate P-limitation is followed by P enrichment under otherwise favourable conditions (temperature, light etc).   Even if bacteria are present in the medium, hormogonia seldom have bacteria firmly attached to the surface.   

    Individual trichomes can be picked up with very fine glass pipettes (drawn out in a bunsen flame), while using a laminar flow hood, and then taken through a series of four to five washes.  It takes a few days practice to get the technique working well.  Trichomes from intermittently moist habitats such as rice-fields usually survive well and it should be possible to obtain 70-80% survival rate.  Trichomes from permanently wet habitats are more of a challenge, though Arthrospira has proved fairly easy.

Brian Whitton

 

 

 

Dear Raza,

Cycloheximide May not be available to all parts of the world, as its supply to some countries is restricted. therefore, serial streaking for the purification of unuicellular and manual picking of  filaments under streomicroscope is a good choice.

 

 

  
نویسنده : رضا رمضان نژاد قادی/ آرش کیانیان مومنی ; ساعت ۱۱:٥۱ ‎ق.ظ روز یکشنبه ۱۱ بهمن ۱۳۸۸
تگ ها : کشت جلبکها

رفع آلودگی قارچی از محیط کشت جلبکی

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مطلب زیر در رابطه با رفع آلودگی قارچی از محیط کشت جلبکی است که بدلیل ابتلای برخی دانشجویان در زیر به آن اشاره شده است. این مطالب در ارتباطات نامه الکترونیک از پروفسور ویتون از انگلستان و پروفسور ریتچی از استرالیا دریافت و منتشر شده است:

1- It is actually, vey hard to remove fungi contamination.  You may be able to find some antibiotic which are only effecting fungi but most of them also kill cyanobacteria.  
another method is to isolate the cyanobacteria under the microscope using a tube + adding these to a sterile culture.  This is a very tiring methodologies but does work.

2- You may try using anifungal agents when during the process of media preparation.I work on Spirulina and use antibiotcis in small amount so that I can get rid of bacteria.

 Another option is introducing nitrates...It kills the rotifiers.

 

3- For unicellular cyanobacteria we've had good luck in purifying them by repeated rounds of streak plates.  We test the resulting isolated colonies for bacterial or fungal contamination by culturing sub-samples on enriched media.  However, it can take several rounds of streak plates to isolate a pure culture.

4- you may try out lactic acid and check out these pages of the Andersen book:

5- 
Try cycloeximide ( a antibiotic for eukaryotic cells). Start with 7.0 mg/liter (final concentration), in the cyanobacteria culture. First you must isolate de cyanobacteria cells, or filaments, and inoculate it in the media with cycloeximide. Good luke

 

6-  I guess I have much more a request to you than an actual answer. We had some problems with fungal contamination in certain samples, and it is indeed a bit hard to get rid of certain contaminations. I am sure that you tried some (if not all) of the following, but here are some suggestions:

- If the microorganism shows phototrophism, that may help to isolate it by illuminating at one side and expecting that the microorganism migrates;

- if the fungus is less resistant to photobleaching, a high irradiance may help isolate the cyanobacteria;

- if the cyanobacteria have air vesicles, as it happens with Spirulina, then maybe successive centrifugations collecting the supernatant could help. Maybe a little detergent would be good in order to break the surface tension.

- If the cyanobacteria have a higher settling velocity than the fungus, centrifugation would still work for enrichment. However, in any case a streaking plate cultivation should be done.

- selective media, including even antifungal agents, could be used if you are targeting some specific features of the cyanobateria (e.g. extremophiles) and depending again on the specific contamination.

- Finally, the fungus being an heterotroph, *maybe* the culture could be enriched in cyanobacteria (and depleted in fungi) if you use really low concentrations of organic carbon, either by frequent reculture, or continuous feed to a small culture flask.

 

I suppose that those fungal contaminations you observe are fast-growing, but maybe streaking-plates may still be your best shot, since it is simple, after perhaps adequate dilution and agitation (or mild sonication) of the sample in order to loose cells.

 

7- No - centrifuging will not do any good. Try 45 to 50 oC.  That kills most fungi.  BGA laugh at that. Also Chloramphenicol will kill fungi. The common fungicide called benlate sometimes works. Common bleach (sodium hypochlirite) will work but you have to wok out an appropriate concentration and dose time.  Light destoys chlorine (Cl2) so you may not have to remove it.

8-  The standard - and very simple - procedure to remove fungi is to use cyclohemiximide to kill eukaryotes. You should be able to find many references to a suitable concentration, but there is usually a huge difference in toxicity, so not particularly critical.  Cyclohexmimide is quite cheap and am sure many researchers will have some - all you need is a few mg.

 

 

 

 

 

 

 

 

 

 

 

 

  
نویسنده : رضا رمضان نژاد قادی/ آرش کیانیان مومنی ; ساعت ۱:٤٥ ‎ب.ظ روز سه‌شنبه ٦ بهمن ۱۳۸۸
تگ ها : کشت جلبکها