Dental calculus. This small, hard, inconspicuous substance that forms on the teeth of humans and animals contains a surprising amount of information about our lives. During its formation and growth... Show moreDental calculus. This small, hard, inconspicuous substance that forms on the teeth of humans and animals contains a surprising amount of information about our lives. During its formation and growth as a living biofilm, it accumulates a wide variety particles, especially bacteria and food debris.What makes this so interesting to archaeologists is that, when plaque hardens and forms dental calculus, these particles become trapped and well-protected against removal and degradation during hundreds to thousands of years, preserving a picture of past activities.The major problem—one of the major problems, for there are several—one of the many major problems is that this picture was never a complete picture of a lifetime of activities, and that picture fades over time. We know that these problems exist and that they limit our interpretations of past activities. What we need to do is approach these problems at a fundamental level. In my dissertation I introduce a protocol for growing artificial dental calculus. Working with a very controlled model allows me to explore the influence of a wide range of factors that may affect the uptake of particles into dental calculus, and better explain why and how our picture is incomplete. Show less
Dental calculus has proven to contain a wealth of information on the dietary habits of past populations. These insights have, to a large extent, been obtained by the extraction and identification... Show moreDental calculus has proven to contain a wealth of information on the dietary habits of past populations. These insights have, to a large extent, been obtained by the extraction and identification of starch granules contained within the mineralised dental plaque from a wide range of regions and time periods. The scope of previous studies have been limited to microfossil extraction and identification to reconstruct dietary preferences from the archaeological record, and few studies have attempted to address the biases of starch retention in dental calculus. Those that have considered this problem have been limited to in vivo studies on modern humans and non-human primates. Here, we present a multispecies oral biofilm model, which allows experimental research on starch incorporation and retention to be conducted on in vitro dental calculus in a controlled laboratory setting. The biofilms were exposed to treatment solutions with known quantities of dietary starches (wheat and potato) during the 25 days growth period. After this, the starch granules were extracted from the mature biofilm (by dissolution in EDTA), and counted. We show that the granule counts extracted from the model dental calculus represented a low proportion (ranging from 0.06% to 0.16%) of the total number of granules exposed to the biofilms throughout the experiment. Additionally, we found that the ratios of granule sizes from the extracted starch granules differed from the original treatment solutions, with large granules (>20 μm) consistently being under-represented. We also found a positive correlation between the absolute granule counts and dry-weight of the biofilm (r = 0.659, 90%CI[0.463, 0.794]), meaning the absolute quantity of starch granules will increase as the size of the calculus deposit increases. A similar, but weaker correlation was found between the concentration (count per mg) of granules and dry-weight (r = 0.3, 90%CI[0.0618, 0.506]). Our results complement and reinforce previous in vivo studies suggesting that dental calculus presents a very small, and partly biased picture of the original dietary intake of starches, with an over-representation of plants producing granules smaller than 20 μm in size. The experimental model presented here is well-suited to address the need for further validation of methods and biases associated with dietary research on dental calculus. Show less
Palaeoanthropologists have proposed that Neanderthals, the Middle Palaeolithic hominin occupant of Eurasia, differed from modern human relatives by having specialised diets focused on big game. A... Show morePalaeoanthropologists have proposed that Neanderthals, the Middle Palaeolithic hominin occupant of Eurasia, differed from modern human relatives by having specialised diets focused on big game. A narrow dietary niche at the top of the terrestrial food chain is inherently prone to instability, potentially contributing to extinction of the Neanderthals. However, limitations in detecting plant consumption imply that scientists are unaware of much of Neanderthal diet. My dissertation revises the role of plants in Neanderthal subsistence using dental calculus, a material that is recognised to contain food traces, as a source of dietary data. To do this I assessed how accurately calculus records diet, by testing it with a variety of techniques on a population of chimpanzees with decades of documented dietary history. Then, my dissertation examined if it is possible to explore the resilience of the Neanderthal dietary niche by assessing for changes in plant use over time. Comparing diets from different habitats, data suggests a broad range of diets on the Mediterranean rim and in the cooler areas of the Neanderthal range. Surprisingly, the study found no evidence of changes in plant dietary breadth despite variation in environments. This stability implies a deeply resilient ecological niche across their range. Show less
Aspergillus niger produces a wide variety of carbohydrate hydrolytic enzymes which have potential applications in the baking, starch, textile, food and feed industries. The goal of this thesis is... Show moreAspergillus niger produces a wide variety of carbohydrate hydrolytic enzymes which have potential applications in the baking, starch, textile, food and feed industries. The goal of this thesis is to unravel the molecular mechanisms of starch and inulin modifying network of A. niger, in order to improve the enzyme production and substrate utilization as well as to find novel enzyme activities. The research described in this thesis shows how we identify genes which encode enzymes involved in starch and inulin catabolism, how they are transcriptionally regulated, as well as how the expressed enzymes react to the carbon sources and what are their physiological roles in A. niger. Important findings are outlined as follows. We have identified inulin pathway activator InuR. The activation of InuR is thought to be triggered by the pathway inducer, sucrose or its derivative, but not previously known fructose. The activated InuR induces the expression of genes encoding inulin modifying enzymes and related sugar transporters in inulin metabolism. In addition, using the tightly regulated inuE promoter combined with racA(G12V) and GFP reporter genes, we set up a novel screening method for isolation of mutants involved in inulin signaling pathway. Show less
