If you can get that kind of performance out of Matlab, then you should be able to simulate every cell of C. elegans in real time with < 1,000 cores with a rewrite in C. Some researchers at the University of Glasgow already have a working 1,000 core processor (using FPGAs). I'm gonna to have to do some updating on this.
The metabolism, anyway. This is a high-level model of the metabolism of a simple bacteria, and I'm not sure how close one could consider it to a neuron which was part of a functioning neural network, for example.
"A Whole-Cell Computational Model Predicts Phenotype from Genotype" by Jonathan Karr et al.
This paper appeared a few days ago in Cell, and describes a computational simulation of the bacterium Mycoplasma genitalium, conducted at this lab. The paper is behind a paywall, but is blogged about here. The simulation software is freely available from the project web site.
From the abstract: "Here, we present a ‘‘whole-cell’’ model of the bacterium Mycoplasma genitalium, a human urogenital parasite whose genome contains 525 genes. Our model attempts to: (1) describe the life cycle of a single cell from the level of individual molecules and their interactions; (2) account for the specific function of every annotated gene product; and (3) accurately predict a wide range of observable cellular behaviors."
According to an editorial commentary in the same issue, this is the first simulation of a complete free-living microbe.