Food issues, please help
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Food issues, please help
by Helen White-Cooper
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Dear all,
We have recently had serious problems with some of our fly stock cultures, and would really like some input into what could be the problem, and how to solve it. We use a standard maize/dextrose/yeast/agar recipe. cooking is done in a large food cooker, typically 40-50 litres per batch. We add propionic acid and nipagen (dissolved in ethanol) just before dispensing. We cook every 3-4 weeks. After dispensing we leave the vials/bottles overnight before plugging. We store cooked food wrapped in autoclave bags at 4C. We leave the food to come to room temperature before use. Fly stocks are cultured in an 18C room, or at room temperature. Last year (september) we bought a new batch of maize. Initially the food was good and all the flies were happy. Over the next few months the quality of the food declined, and stocks began to suffer. By March this year we had big problems. In the most seriously affected stocks the adults died after being put on the new food. In other stocks the flies were alive, laid eggs, but no eggs hatched. In many stocks eggs hatched (at least some did), but it would be 4 weeks or more before adults eclosed (rather than the expected 3 weeks). Some stocks were unaffected. We bought new maize (March 09), and the problem went away, BUT, over the next few months (june/july) it came back... So, we thought it was due to maize going off, and switched to another batch, this one had been bought a while ago, used with no problems and stored at -20, so should stay fresh. Again, initially (july) everything was fine, but now the stocks are slowing their generation times / dying off again. We have had the first batch of maize tested for pesticide residue but it came back negative. We have also tested it for Bt spore contamination (yes it is organic...), by heating a maize /water mix to 80C for 15 minutes and plating on media suitable for Bt. we do not get Bt growth, however there is growth of something (fungal). we have tested this with flies in a laying bottle and it does not seem to retard egg hatching, neither is it toxic to adults or larvae (indeed the larvae love it...). So, does anyone out there have any ideas what could be causing the problem, and most importantly, how to make it go away? The only things we can think of are the temperature the food gets to after adding the maize/ sugar/ yeast mixture (might it have to get up to 85C?, ours probably only gets to 80C), should we add the nipagen earlier (could the ethanol be causing the problem?). Yours in desperation Helen -- Dr Helen White-Cooper School of Biosciences Museum Avenue Cardiff University Cardiff CF10 3AX Tel 029 20875492 _______________________________________________ Dros mailing list Dros@... http://www.bio.net/biomail/listinfo/dros |
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RE: Food issues, please help
by Hans Bakker-2
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Dear Helen
Dear Helen Do you see something in your cultures? We had problems with the development of a slimy layer of bacteria or fungi in the vails. Our problem was solved by using more Nipagen/methyl paraben (1 gr/liter), wich I think you should indeed ad late as it is heat sensitive. Our protocol was not so clear about the amount and we were using much less before, but I see also protocols using 2-3 gr/liter. If not all stocks are affected, it might rather be something carried by the flies than comming from the food. Good luck, Hans Dr. Hans Bakker Hannover Medical School Dept. Cellular Chemistry OE4330 Build. I3, Level 2, Room 3110 Carl-Neubergstrasse 1 30627 Hannover, Germany bakker.hans@... +49.511.5328245 -----Original Message----- From: dros-bounces@... [mailto:dros-bounces@...] On Behalf Of Helen White-Cooper Sent: Tuesday, September 15, 2009 3:39 PM To: dros@... Subject: [Drosophila] Food issues, please help Dear all, We have recently had serious problems with some of our fly stock cultures, and would really like some input into what could be the problem, and how to solve it. We use a standard maize/dextrose/yeast/agar recipe. cooking is done in a large food cooker, typically 40-50 litres per batch. We add propionic acid and nipagen (dissolved in ethanol) just before dispensing. We cook every 3-4 weeks. After dispensing we leave the vials/bottles overnight before plugging. We store cooked food wrapped in autoclave bags at 4C. We leave the food to come to room temperature before use. Fly stocks are cultured in an 18C room, or at room temperature. Last year (september) we bought a new batch of maize. Initially the food was good and all the flies were happy. Over the next few months the quality of the food declined, and stocks began to suffer. By March this year we had big problems. In the most seriously affected stocks the adults died after being put on the new food. In other stocks the flies were alive, laid eggs, but no eggs hatched. In many stocks eggs hatched (at least some did), but it would be 4 weeks or more before adults eclosed (rather than the expected 3 weeks). Some stocks were unaffected. We bought new maize (March 09), and the problem went away, BUT, over the next few months (june/july) it came back... So, we thought it was due to maize going off, and switched to another batch, this one had been bought a while ago, used with no problems and stored at -20, so should stay fresh. Again, initially (july) everything was fine, but now the stocks are slowing their generation times / dying off again. We have had the first batch of maize tested for pesticide residue but it came back negative. We have also tested it for Bt spore contamination (yes it is organic...), by heating a maize /water mix to 80C for 15 minutes and plating on media suitable for Bt. we do not get Bt growth, however there is growth of something (fungal). we have tested this with flies in a laying bottle and it does not seem to retard egg hatching, neither is it toxic to adults or larvae (indeed the larvae love it...). So, does anyone out there have any ideas what could be causing the problem, and most importantly, how to make it go away? The only things we can think of are the temperature the food gets to after adding the maize/ sugar/ yeast mixture (might it have to get up to 85C?, ours probably only gets to 80C), should we add the nipagen earlier (could the ethanol be causing the problem?). Yours in desperation Helen -- Dr Helen White-Cooper School of Biosciences Museum Avenue Cardiff University Cardiff CF10 3AX Tel 029 20875492 _______________________________________________ Dros mailing list Dros@... http://www.bio.net/biomail/listinfo/dros _______________________________________________ Dros mailing list Dros@... http://www.bio.net/biomail/listinfo/dros |
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