We had certainly tried that: spreading/streaking on KA 
plates and picking growing edge as well as spores. Did not 
help against the small, slow growing monster bugs!

Would be nice to post here if there is a solution other 
than waiting until it goes away by itself!
wolfgang


On Sun, 10 Nov 2013 08:08:39 +1100
  Professor Paul Fisher <[log in to unmask]> wrote:
> Ricki could be right - maybe Dicty is producing thema 
>out ages in culture.
> Dan's suggestion is good except I would not just let 
>them grow across the
> plate as that selects for fast spreading, poorly 
>aggregating variants. I
> would always streak out for single colonies/plaques of 
>Dicty on the
> bacterial lawn....just like purifying a bacterial 
>strain/transformant.
> Plate the bacterial food source first as a lawn and dry 
>it in the laminar
> flow hood, then streak out the Dicty. Do this a few 
>times serially and you
> should be able to get away from any contaminant. On each 
>passage do the
> next subculture as soon as your single plaques are a few 
>mm
> diameter....gives the contaminants less chance and less 
>likely to select
> Dicty morphological variants.
> 
> Cheers
> Paul
> 
> Sent from Samsung mobile.
> Professor Paul R. Fisher
> Chair in Microbiology
> Deputy Dean
>Faculty of Science Technology & Engineering
> La Trobe University.
> On Nov 9, 2013 3:29 AM, "Richard Sucgang, PhD" 
><[log in to unmask]> wrote:
> 
>> This sounds familiar - I think I recall someone 
>>reporting Dicty blebbing
>> off small membrane bound vesicles. It may be that what 
>>you are seeing isn't
>> so much contamination but some kind of physiological 
>>peculiarity of sick
>> Dicty cells. That is, instead of them killing Dicty, 
>>it's actually a
>> symptom of the Dicty cells dying.
>>
>> > On Nov 8, 2013, at 9:32 AM, "Damer, Cynthia Kay" 
>><[log in to unmask]>
>> wrote:
>> >
>> > Dear Colleagues,
>> >
>> > My lab is currently experiencing a culture 
>>contamination problem that I
>> have not experienced previously.  We are culturing Dicty 
>>in HL-5
>> supplemented with penicillin and streptomycin on plastic 
>>sterile culture
>> dishes.  The contaminant appears to be very small (less 
>>than a micron) and
>> spherical and is not able to move.  In addition, it is 
>>very slow growing.
>>  However, as the contaminant becomes more numerous, the 
>>Dicty cells become
>> rounded and eventually die.  Unfortunately, even when we 
>>thaw out strains
>> in new media, the contaminate appears again.  We've also 
>>tried centrifuging
>> and washing many times and greatly diluting the 
>>cultures.  This seems to
>> get rid of most of it, but it eventually grows up again.
>> >
>> > Any advice would be appreciated.
>> >
>> > Thanks,
>> >
>> > Cynthia
>> >
>> > Cynthia K. Damer
>> > Professor
>> > Biology Department
>> > Brooks Hall Room 229
>> > Central Michigan University
>> > Mount Pleasant, MI 48859
>> > (989) 774-3455
>>

Wolfgang Nellen
Abt. Genetik
Univ. Kassel
Heinrich-Plett-Str. 40
34132 Kassel
Germany