I also observed the similar dots in my Caco-2 culture. But these are normal. The number of dots per cell is higher if the cells are stressed, i.e. during reviving cells. Once the cells start growing, in next 2 passages the number of dots decreases drastically but will not completely disappear. 

I also see the similar dots in HCT-116, Thp1, U937, A549 cell lines, but number is less than Caco-2.

Have you cultured Caco-2 cells? How does it look to you should be of major concern.

Coming to these black dots  or granular appearance with in the cells are only observed at higher magnification i.e. 20X or more.

Such dots can also be observed with other cell lines like MCF7, MDA-MB-231 and others which I am handling currently. So this is normal unless an until the size or these dots increased which is an indication of unhealthy cells.

Hope you got your answer.

I also observed the similar dots in my Caco-2 culture. But these are normal. The number of dots per cell is higher if the cells are stressed, i.e. during reviving cells. Once the cells start growing, in next 2 passages the number of dots decreases drastically but will not completely disappear. 

I also see the similar dots in HCT-116, Thp1, U937, A549 cell lines, but number is less than Caco-2.

thank all of you.Jaykumar Kambli and Biswaranjan Pradhan

I am culturing Caco-2 cells now,but it seems to grow slowly and the black dots are more than the image from ATCC,especially between the cells.I am not sure they are normal or contamination.

These black dots are very likely to be stress granules. I have noticed they were markedly increased after thermal shock (thawing frozen cells, for instance). By definition, stress granules are transient entities composed of proteins and mRNAs resulting from a stress-induced translation initiation repression. For more info, check out the following articles:

1. Kedersha N, Anderson P (2007) Mammalian stress granules and processing bodies. Methods Enzymol 431: 61–81

2. Anderson P, Kedersha N (2008) Stress granules: the Tao of RNA triage. Trends Biochem Sci 33: 141–150.

3.Decker CJ, Parker R (2012) P-bodies and stress granules: possible roles in the control of translation and mRNA degradation. Cold Spring Harb Perspect Biol 4: a012286.

Are you cells stressed with you?

About your slo-growing CaCO-2 cells, be sure you are using DMEM high-glucose supplemented with 10%FBS. CaCO-2 cells only grown fast if you let them sugar high! 

Hi, i am currently culturing caco-2 in my lab. Just purchased it from ATCC.. attach herewith my microphotograph of my Caco-2 at passage one for your comparison. i also observed the dots but mostly in the cells not between the cells. it may indicate the cells are under stress at early passage. Yes it grows very slow at first  it takes 8 days for it to attached and confluence.. but in the next subculture i found out that they grow very fast. i subs them every 3 days at 1:4 ratio. EMEM is fine at first. but them i shifted to DMEM (high sugar media) as suggested by literature for a good caco-2 practice.

This can a be a novel cell culture contamination

Please see below:

Biologicals. Author manuscript; available in PMC 2011 Mar 1.

Published in final edited form as:

Biologicals. 2010 Mar; 38(2): 273–277.

Published online 2009 Nov 18. doi: 10.1016/j.biologicals.2009.09.006

PMCID: PMC2849847

NIHMSID: NIHMS151316

Got black swimming dots in your cell culture? Identification of Achromobacter as a novel cell culture contaminant

Jennifer Sue Gray,1,* Janette Marie Birmingham,1,* and Jenifer Imig Fenton1,2

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2849847/

in fact, they are contiminant.