diploid, these xenopus have four homologous copies of each chromosome and thus, proteins derived may have a different function. More research is needed to examine the protein production of X. laevis systems. Mammalian Cells Although mammalian cells are cultured with more difficulty, are time-consuming, require more nutrients, and are significantly more costly, a protein that requires post-translational modifications must be expressed in mammalian cells to protect the clinical efficacy and fidelity of the product. However, even between mammalian cells, there are observed differences, for example differences in glycosylation between rodent and human cells. Even within one cell line, often stabilizing a cell line results in modified glycosylation patterns. The only commercially viable way to use mammalian cells as host systems is a high value end product. Common mammalian cell lines, especially in research include the COS-7 from Cercopithecus aethiops monkey, CHO from the Cricetulus griseus hamster, and the HEK293 human kidney line. Protists A common protist eukaryotic expression system is the slime mold, Dictyostelium discoideum, and is unique as it has a circular plasmid, packaged similarly to chromatin. As a simple eukaryotic haploid organism, it can grow in high concentrations without the expensive conditions of mammalian cell culture, and perform post-translational modifications. The protein itself is expressed in several forms including as membrane attached, secreted, or cell associated, and can glycosylate protein product. Filamentous Fungi Fungi are natural decomposers of many ecosystems. As a result, it is able to secrete large amounts of enzymes, more so than bacterial based systems. However, utilizing fungi as expression systems has seen several barriers, especially due to the lack of knowledge regarding fungal genetics due to its inherent complexity. The filamentous fungi specifically have been a host system of interest, and includes Penicillium (where penicillin was derived), Trichoderma reesei, and Aspergillus Niger. Filamentous fungi are efficient at producing extracellular proteins, bypassing the additional step of cell breaking to extract proteins. Some also have inexpensive growth and media conditions. Fungi also contain glycolysation and modification capabilities that are helpful for eukaryotic proteins. Additionally, they have also successfully produced vaccine related proteins, and some filamentous fungi have been deemed GRAS by the FDA. However, the major drawback of using this host system is that yields are extremely low and not economically viable. Moreover, the low amount of protein that is produced is often degraded by fungal proteases. Some approaches to address this have been using protease