How's your immune system doing? Candida albicans knows.

Chances are it is inside you right now, waiting. The moment you let your guard down Candida albicans will be there to spring into action. This versatile fungus can grow both as a yeast and pseudohyphally and it knows how healthy you are.

White and Opaque versions of Candida albicans

Candida albicans normally colonizes our bodies without symptoms; but when your immune system becomes compromised it takes quick advantage and moves on the offensive, generally causing minor infections but capable of much deadlier ones.

But how does it know what is up? A study published in mBio looks to answer that very question.

Variation in Candida albicans EFG1 Expression Enables Host-Dependent Changes in Colonizing Fungal Populations

Growing C. albicans in mice with healthy and immunodeficient mice, the team hoped to compare growth patterns and phenotypic variants, concentrating largely on transcription factor Efg1p activity.
Efg1p is an important physiological regulator for C. albicans and earlier studies have demonstrated that it influences the harmful potential that the fungal cell has.

In this study the scientists show that it also regulates colonization dynamics, having different expression and activity in individual cells throughout. Their study also demonstrates how the host environment changes the C. albicans population composition, thus changing the colonizer's physiology.

To test the growth rates of C. albicans with different levels of Efg1p the researchers basically fed healthy and immunosensitive mice with strains of C. albicans that had both low and high expression of the transcription factor. Then they counted fecal pellets for colonization patterns.

As it turns out those mice with strong immune systems showed a higher growth of cells with a high expression of Efg1p and those with a compromised immune system showed larger growth of those with low activity. The scientists propose that in a general,  there is a heterogeneous population growth. With that expression as the C. albicans comes into contact with an immune system it can adjust its physiology to be most productive despite the varying levels of immune system health.

What this could mean is that as the host's immune system becomes less affective the larger population of low Efg1p active cells will show a spike in growth, thus setting up the colony for engaging in pathogenic actions.

So, in the end,  measuring the ratio of high and low active Efg1p cells in a system could help to us determine host immune status as well as develop new methods for detecting and fighting Candida caused infections before they become severe or deadly.

This study gives us a small insight to how we can keep an eye on one fungus that is just waiting for us to falter.


Citation:
Jessica V. Pierce, & Carol A. Kumamoto (2012). Variation in Candida albicans EFG1 Expression Enables Host-Dependent Changes in Colonizing Fungal Populations mBio DOI: 10.1128/​mBio.00117-12

Photo: Rebecca E. Zordan, Mathew G. Miller, David J. Galgoczy, Brian B. Tuch, Alexander D. Johnson via http://en.wikipedia.org/wiki/File:Whiteopaquecandida.jpg