Beyond ancient microbial DNA: nonnucleotidic biomolecules for paleomicrobiology

Identifying the causes of past epidemics depends on the specific detection of pathogens in buried individuals; this field of research is known as paleomicrobiology, an emerging field that has benefited from technological advances in microbiology. For almost 15 years, the detection, identification, and characterization of microbes in ancient environmental and human specimens emerged on the basis of ancient DNA (aDNA) analyses. aDNA limitations due to potential contamination by modern DNA and altered aDNA led to the development of alternative methods for the detection and characterization of nonnucleotidic biomolecules, including mycolic acids (of ancient mycobacteria) and proteins. Accordingly, immunohistochemistry, immunochromatography, and enzyme-linked immunosorbent assay techniques have been developed for the specific detection of microbes from ancient human and environmental specimens. Protein analysis by mass spectrometry, a standard for ancient animal identification, has also recently emerged as a technique for ancient mycobacteria detection, while immuno-PCR is yet another promising technique. As with aDNA, strict protocols must be enforced to ensure authenticity of the data. Here we review the analysis of nonnucleotidic biomolecules from ancient microbes and the ability of these analyses to complement aDNA analyses, which opens new opportunities for identification of ancient microbes as well as new avenues to potentially resolve controversies regarding the cause of some historical pandemics and study the coevolution of microbes and hosts.