Electron-microscopical and light-microscopical studies in bacterial cytology

PART I. A STUDY OF THE FACTORS INFLUENCING THE PRODUCTION OF VOLUTIN IN AEROBACTER AEROENES: 1. Aero.aerogenes A3, an organism which does not produce volutin under normal conditions of culture, was found to produce volutin under three different special conditions namely (1) at the acid reaction developed during growth on a poorly -buffered sugar containing medium, (2) by growth on a medium deficient in either its nitrogen or sulphur source and (3) on transfer of phosphate- starved cells from a "First Medium" deficient in phosphate to a "Second Medium" rich in phosphate. The volutin produced under all three cultural conditions was found to react metachromatically with methylene blue - the characteristic property of the volutin found in 0.diphtheriae and Sp.volutans. Thus the volutin of Aero.aerogenes was thought to be of the same nature as the classical volutin. The volutin granules of :zero.aeroenes were also observed in unstained, wet films by the phase contrast microscope, demonstrating that the granules were not staining artefacts. 2(a) When Aero.aerógenes I3 was grown aerobically at 35°C on a 0.1 per cent glucose medium the growth was maximal when the phosphate content was 0,1 per cent or greater; the pII did not fall below 6.1 and no - 109 - volutin was produced. 'Alen the phosphate content of the medium was between 0.001 and 0.03 per cent, and no other buffer was present, the pH fell to 4.5 or less, and much volutin was produced in 24 hours. This fall in pH of the medium was found to be the determining factor for the volutin production since (1) when "citrate "or bicarbonate buffer was added to a medium containing 0.01 per cent phosphate the pH did not fall below 6.0 and volutin production was prevented, and (2) when 1.0 per cent pH 5.2 acid phosphate (ILH.2PO4) was substituted for 1.0 per cent pH 7.3 phosphate mixture the pH fell to 4.5 and abundant volutin was produced. (b) When the phosphate content of the unbuffered medium was less than 0.0003 per cent, the amount of growth was reduced even further and the pH again fell to 4.5 or less but no volutin was produced. Such cells were found to be "nuclear" indicating that they were phosphate- starved. This showed that a certain amount of phosphate was necessary for the production of volutin. (c) The substitution of various other energy sources which did not cause such a large drop in the pH of the medium resulted in a smaller volutin production. This together with the fact that - 110 - volutin only disappeared with the occurrence of cell division would show that volutin was á metabolic -product. 3(a) When the organisms were grown at 350C on a nitrogen or sulphur -deficient medium buffered at neutral pH "nuclear" volutin -containing cells were produced in 24 hours but a deficiency in the phosphate or carbon and energy source did not induce a similar production :of volutin. (b) The subculture of such nitrogen- and sulphur- deficient cells on a fresh medium resulted in the loss of the volutin only after a few hours when cell division had occurred. The transfer of the "nuclear" non -volutin containing phosphate - starved cells to a fresh phosphate containing medium resulted in abundant volutin production. 4(a) When Áero.aerogenes was grown on a series of buffered media containing 0.1 per cent glucose and various amounts of phosphate, it was found that the cells were "nuclear" in appearance and the growth was curtailed on media containing 0.0003 per cent phosphate or less. Only these phosphate- starved produced volutin on transfer to a fresh medium containing phosphate. This volutin production was apparent after 3 minutes subculture, rose to a - 111 - maximum at 2 hours and disappeared mainly within 8 hours. 'he disappearance of the volutin again appeared to be accompanied with the return of the normal staining reaction to the cells and with the occurrence of cell division. (b) If no phosphate were added to the "Second Medium" no volutin was produced on transfer of phosphate- starved cells. Therefore phosphate was required for the production of volutin. (c) Likewise the total omission of glucose from the "Second Medium" caused a complete absence of the volutin production but other components of the glycolysis cycle were found to support volutin production in the "Second Medium ". Therefore glucose or another carbon and energy source was required in the "Second Medium" for the production of volutin. (d) The presence of ammonium sulphate, potassium and magnesium ions was found to be required for maximal volutin production. 5. As phosphate seemed to be required for the production of volutin the ratio of phosphorus to nitrogen was determined for the volutin -free and volutin -rich cells produced under the different cultural conditions. In all cases it was found -112- that the ratio of total phosphorus to total nitrogen for the volutin-rich cells was almost twice that of the volutin -Free cells. .'hen the cells were fractionated and the phosphorus content of each fraction estimated, nine of the ten fractions of the volutin -rich cells were found to contain double the amount of phosphorus present in the corresponding fraction of the volutin -free cells while the remaining fraction R9 of the volutin -rich cells showed a forty -fold increase over that of the volutin -free cells. . In the phosphate- starved cells which were transferred to the phosphate containing medium the phosphorus content of the fraction R9 was found to follow the same pattern as the volutin production in that it rose to a maximum in 30 minutes and thereafter fell away to practically none at 180 minutes. 6. Volutin in Äero.aerogenes appears to be a normal metabolic product which contains phosphorus - probably metaphosphate and which is. only observed when some enzyme systems are blocked due to growth under adverse cultural conditions.PART II. A STUDY OF THE MOTILITY AND FLAGELLATION OF AEROBACTER CLOACAE AND ESCHERICHIA COLI STRAINS: 1. In all the Aero.cloacae and Esch.coli strains examined a direct correlation of the motility of young cultures as observed by the hanging drop method and the presence of flagella as seen in electron microscope preparations was obtained. Photographs are shown to illustrate the presence or absence of the flagella in some of the Aero.cloacae strains and in all of the Esch.coli A strains. 2. It was found that if a peptone water culture of Esch.coli A was incubated for 16 hours instead of 6 hours the motility was much reduced but that the flagella were still present when the organism was examined by the electron microscope. This means that the flagella become inactive in older cultures. 3. `hen the organisms were cultivated in liquid synthetic media, the flagella were still found but the motility was absent. The cause of this is not known with certainty but it may have been the lack of some essential growth factor. 4. The addition of phenol to peptone water caused loss of both motility and flagella. In synthetic liquid media the phenol had less effect. 5. ';Then the organisms were grown on solid media (peptone agar) virtually the same results were obtained for these cultures as for the peptone water cultures which were incubated for the same length of time (16 hours). Here the motility was feeble but the flagella were produced if the organis was 'motile' (i.e. motile at 6 hours in peptone water). 6. Irregular filaments were found on certain of the organisms when they were grown either in peptone water or synthetic media. 'These appendages which were named pseudoflagella were short, angular filaments of uneven diameter and were discrete in that they did not merge into one another when they crossed. They were not general features of this group of organisms as all the species did not produce them, neither were they produced due to the motility of the organism as some motile organisms did not exhibit them while some non -motile ones produced them in abundance. Similarly the pseudoflagella did not appear to be slime threads since they were not produced by all the slime - formers but were produced by some of the non - slime- formers. It was found, however, that those organisms which produced pseudoflagella were also capable of agglutinating guinea pig and fowl red blood cells and that those which did not exhibit pseudoflagella had no effect on the red blood cells. The pseudoflagella reacted to phenol in the same manner as the flagella so they may be of the same chemical nature i.e. prótein. It is suggested that the pseudoflagella might be extracellular enzyme bearing structures

Did the Curtailing of the Stop, Question, and Frisk Policy Lead to An Increase in New York City\u27s Homicide Rate in 2015?: An Examination of the Relationship Between Stop-and-Frisk and Violent Crime Rates

This thesis is an examination of the relationship between the New York Police Department\u27s Stop, Question, and Frisk policy and the city\u27s homicide rates. Using a historical analysis of NYC crime data as well as a cross-city comparison of homicide rates across the United States, I determine whether or not there is a consistent, causal relationship between the policy and the city\u27s violent crime rates

Low degree points on curves

In this paper we investigate an arithmetic analogue of the gonality of a smooth projective curve $C$ over a number field $k$: the minimal $e$ such there are infinitely many points $P \in C(\bar{k})$ with $[k(P):k] \leq e$. Developing techniques that make use of an auxiliary smooth surface containing the curve, we show that this invariant can take any value subject to constraints imposed by the gonality. Building on work of Debarre--Klassen, we show that this invariant is equal to the gonality for all sufficiently ample curves on a surface $S$ with trivial irregularity.Comment: 14 pages, comments welcome

Development of a Team Human Reliability Tool (ROCCI)

Human Reliability Assessments (HRA) have been developed so designers and users can understand how likely it is for a human to make an error when using a product or system in the workplace. This is called the reliability of the product. Approximately twenty-six techniques exist to assess the reliability of an individual human in a process. However, often a team of people interact within a system and not just one individual on their own. Hence a new generation of HRAs is needed to assess the effects of teamwork on reliability. This EPSRC CASE studentship, supported by BAE systems, develops a prototype, which enables a designer to quantify and answer to the question: “If I allocate this team to execute that task in System X, how likely is it that they will succeed?” This prototype assumes that a process can be defined in the form of a flow diagram and that roles can be allocated to execute it. Then, using one of those twenty-six techniques, individual reliabilities can be calculated. These are then modulated, by considering how the team interaction affects the three core elements of Trust, Communication and Decision Making Power Distance. This creates an ‘interactive reliability’ factor for each individual in the team. These individual reliability factors are combined according to the team architecture for the process in order to determine the overall team reliability factor. The methods of development include: stakeholder interviews; the evolution of requirements specification; sensitivity analysis; and a stakeholder review of the tool. The information from these analyses produced a model about team interaction and the requirements for the new tool together with statements and algorithms that need to be used in the new tool: ROCCI. This technique is useful for use in the early stages of the design process. The successful prototype can be extended into applications for operations and used to assess and adapt products and systems, which involve teams

Facing the emergent digital-informational divide. Informational culture: the case of university library users.

pp. 159-16

Expression profiling of human melanocytes in response to UV-B irradiation

AbstractA comprehensive gene expression analysis of human melanocytes was performed assessing the transcriptional profile of dark melanocytes (DM) and light melanocytes (LM) at basal conditions and after UV-B irradiation at different time points (6, 12 and 24h), and in culture with different keratinocyte-conditioned media (KCM+ and KCM−). The data, previously published in [1], have been deposited in NCBI's Gene Expression Omnibus (GEO accession number: GSE70280)

Economic resilience and crowdsourcing platforms

The increased interdependence and complexity of modern societies have increased the need to involve all members of a community into solving problems. In times of great uncertainty, when communities face threats of different kinds and magnitudes, the traditional top-down approach where government provides solely for community wellbeing is no longer plausible. Crowdsourcing has emerged as an effective means of empowering communities with the potential to engage individuals in innovation, self-organization activities, informal learning, mutual support, and political action that can all lead to resilience. However, there remains limited resource on the topic. In this paper, we outline the various forms of crowdsourcing, economic and community resilience, crowdsourcing and economic resilience, and a case study of the Nepal earthquake. his article presents an exploratory perspective on the link can be found between crowdsourcing and economic resilience. It introduces and describes a framework that can be used to study the impact of crowdsourcing initiatives for economic resilience by future research. An initial a set of indicators to be used to measure the change in the level of resilience is presented.info:eu-repo/semantics/publishedVersio

We\u27ve Failed at Diversifying Our Librarian Ranks, Now What ? A Plan for Addressing the Pipeline Problem

Like many libraries, at our library, we have tried for many years to racially diversify our profession. One of our librarians even made it to the Library Journal Movers & Shakers list for raising awareness of the library profession to students of color through presentations, videos, dinners, and icebreaking activities. But despite our intentions and past efforts, the situation has not improved significantly. Let\u27s face it, we have all failed miserably: currently, the racial composition of librarianship, both at our library and in the librarian profession-at-large, is woefully unrepresentative of the United States’ population. Moreover, despite numerous analyses of this problem over the past decades, the demographics have remained stagnant. For example, for the past decade, our staff of roughly 40 professional librarians has not included any African American librarians. The Institute of Museum and Library Services tweeted a graph in November 2017, showing that the problem is nation-wide (see: https://twitter.com/US_IMLS/status/927922066896146432). Although we might take comfort in knowing that it\u27s not just us — that the profession as a whole has not been able to diversity its ranks — at our library we are not satisfied by the reason that many leaders in our field give for the whiteness of our profession, namely that the issue is simply a lack of a diverse MLS holders. At our library, we are attempting to address this problem at the root, by making graduate school in library science more financially accessible to people of color. This past year and a half, a group of library staff have worked out a proposal for a Post-Baccalaureate Diversity Recruitment Fellowship in which participants would have their tuition and educational expenses financially covered while attending library school and working at our library. The aim is to recruit people of color into the field of librarianship, thus increasing the pool of librarians of color both at our library and in the profession at large by removing the financial barrier of the cost of attaining a graduate dress in Library and Information Studies. We will outline the previous approaches as well, so that we can learn collectively about what did not work. For example, over the years, we held recruitment events for students of color; we post our jobs to listservs of the library ethnic caucuses; we have included diversity language in our recruitment and personnel materials. What we have found is that some of the efforts were inconsistent, not fully supported by library administrations, or simply not bold or big enough. There are other reasons that we will also discuss. Takeaways: -A positive new idea – a Diversity Fellowship that has been fleshed out in a proposal template that we will share. -Work on this proposal has established inclusion as a priority for library staff, catching the attention of the Dean who has looked for ways to make this a reality