Memory shapes microbial populations

Correct decision making is fundamental for all living organisms to thrive under environmental changes. The patterns of environmental variation and the quality of available information define the most favourable strategy among multiple options, from randomly adopting a phenotypic state to sensing and reacting to environmental cues. Cellular memory—the ability to track and condition the time to switch to a different phenotypic state—can help withstand environmental fluctuations. How does memory manifest itself in unicellular organisms? We describe the population-wide consequences of phenotypic memory in microbes through a combination of deterministic modelling and stochastic simulations. Moving beyond binary switching models, our work highlights the need to consider a broader range of switching behaviours when describing microbial adaptive strategies. We show that memory in individual cells generates patterns at the population level coherent with overshoots and non-exponential lag times distributions experimentally observed in phenotypically heterogeneous populations. We emphasise the implications of our work in understanding antibiotic tolerance and, in general, bacterial survival under fluctuating environments

‘Sometimes there’s racism towards the French here’: xenophobic microaggressions in pre-2016 London as articulations of symbolic violence

This article discusses xenophobic microaggressions (Pierce, 1970) experienced by members of the French community in London prior to the EU-Membership Referendum in 2016. Acting at the interface of agency and passivity, implicitness and complicity, they go unseen in the social space despite their omnipresence. Through a close reading of empirical data collected as part of an ethnographic study, the article posits that these microaggressions are articulations of historically embedded anti-French ‘symbolic violence’ (Bourdieu and Wacquant, 1992; Bourdieu, 1993). The three main areas addressed are humour, intersectionality and the reproductive nature of the phenomenon (Bourdieu and Passeron, 1970; Bourdieu, 1972)

Metabolic Adaptation of Ralstonia solanacearum during Plant Infection: A Methionine Biosynthesis Case Study

MetE and MetH are two distinct enzymes that catalyze a similar biochemical reaction during the last step of methionine biosynthesis, MetH being a cobalamin-dependent enzyme whereas MetE activity is cobalamin-independent. In this work, we show that the last step of methionine synthesis in the plant pathogen Ralstonia solanacearum is under the transcriptional control of the master pathogenicity regulator HrpG. This control is exerted essentially on metE expression through the intermediate regulator MetR. Expression of metE is strongly and specifically induced in the presence of plant cells in a hrpG- and metR-dependent manner. metE and metR mutants are not auxotrophic for methionine and not affected for growth inside the plant but produce significantly reduced disease symptoms on tomato whereas disruption of metH has no impact on pathogenicity. The finding that the pathogen preferentially induces metE expression rather than metH in the presence of plant cells is indicative of a probable metabolic adaptation to physiological host conditions since this induction of metE occurs in an environment in which cobalamin, the required co-factor for MetH, is absent. It also shows that MetE and MetH are not functionally redundant and are deployed during specific stages of the bacteria lifecycle, the expression of metE and metH being controlled by multiple and distinct signals

Bacteria-inducing legume nodules involved in the improvement of plant growth, health and nutrition

Bacteria-inducing legume nodules are known as rhizobia and belong to the class Alphaproteobacteria and Betaproteobacteria. They promote the growth and nutrition of their respective legume hosts through atmospheric nitrogen fixation which takes place in the nodules induced in their roots or stems. In addition, rhizobia have other plant growth-promoting mechanisms, mainly solubilization of phosphate and production of indoleacetic acid, ACC deaminase and siderophores. Some of these mechanisms have been reported for strains of rhizobia which are also able to promote the growth of several nonlegumes, such as cereals, oilseeds and vegetables. Less studied are the mechanisms that have the rhizobia to promote the plant health; however, these bacteria are able to exert biocontrol of some phytopathogens and to induce the plant resistance. In this chapter, we revised the available data about the ability of the legume nodule-inducing bacteria for improving the plant growth, health and nutrition of both legumes and nonlegumes. These data showed that rhizobia meet all the requirements of sustainable agriculture to be used as bio-inoculants allowing the total or partial replacement of chemicals used for fertilization or protection of crops

Darwin was right: where now for experimental evolution?

Over the last two decades interest in direct realisation of evolutionary process and the possibilities presented by real time evolution experiments with microbes have escalated. Long-term selection experiments with bacteria have made increasingly transparent the process of evolution by natural selection. In this short article we consider what next for the field and do so by highlighting two areas of interest: the genotype-to-phenotype map and the constraints it imposes on evolution, and studies on major evolutionary transitions and in particular the importance of selection working over more than one timescale. The latter we discuss in light of new technologies that allow imposition of Darwinian properties on populations and communities and how this allows exploration of new avenues of research. We conclude by commenting on microbial communities and the operation of evolutionary processes that are likely intrinsic — and specific — to communities. © 2017 Elsevier Lt

Repeated phenotypic evolution by different genetic routes in Pseudomonas fluorescens SBW25

Repeated evolution of functionally similar phenotypes is observed throughout the tree of life. The extent to which the underlying genetics are conserved remains an area of considerable interest. Previously, we reported the evolution of colony switching in two independent lineages of Pseudomonas fluorescens SBW25. The phenotypic and genotypic bases of colony switching in the first lineage (Line 1) have been described elsewhere. Here, we deconstruct the evolution of colony switching in the second lineage (Line 6). We show that, as for Line 1, Line 6 colony switching results from an increase in the expression of a colanic acid-like polymer (CAP). At the genetic level, nine mutations occur in Line 6. Only one of these—a nonsynonymous point mutation in the housekeeping sigma factor rpoD—is required for colony switching. In contrast, the genetic basis of colony switching in Line 1 is a mutation in the metabolic gene carB. A molecular model has recently been proposed whereby the carB mutation increases capsulation by redressing the intracellular balance of positive (ribosomes) and negative (RsmAE/CsrA) regulators of a positive feedback loop in capsule expression. We show that Line 6 colony switching is consistent with this model; the rpoD mutation generates an increase in ribosomal gene expression, and ultimately an increase in CAP expression

PENINGKATAN PRODUKTIVITAS INDUSTRI CINCAU MELALUI PENERAPAN ALAT PEMERAS MEKANIS

UKM / UD / Home Industri Cincau Jun-Jun merupakan industri penghasil cincau yang terletak di Desa Plantaran, Kaliwungu, Kabupaten Kendal dengan kapasitas produksinya hanya mencapai 468 kg (26 blok). UKM Cincau Jun-Jun merupakan industri cincau satu-satunya di wilayah Kendal, Semarang dan sekitarnya yang masih bertahan memproduksi cincau. Apabila tidak dilestarikan lama-kelamaan keberadaan cincau tersebut akan semakin langka. Produksi Cincau ini masih sangat sangat terbatas kualitas dan kuantitasnya, hal ini disebabkan karena masih sederhananya proses dan peralatan, minimalnya sumber daya manusia, serta permodalan yang terbatas dan dikelola secara konvensional. Permasalahan utama terhambatnya produktivitas UKM ini adalah pada proses produksi yang masih sangat sederhana, khususnya pada proses pengambilan ekstrak bahan baku. UKM tersebut hanya menggunakan saringan sederhana tanpa ada upaya pemerasan bahan baku. Sehingga untuk memisahkan ekstrak dan ampas, bahan yang sudah direbus hanya disaring begitu saja. Tidak mungkin bahan diperas secara manual dengan menggunakan tangan karena bahan tersebut dalam keadaan panas. Oleh karena itu ekstrak yang dihasilkan tidak maksimal karena sebagian ekstrak masih terkandung dalam ampas yang kemudian dibuang. Untuk mengatasi masalah tersebut, UKM memerlukan suatu alat pemeras mekanis dengan desain dan kondisi proses yang disesuaikan dengan keadaan UKM. Melalui alat pemeras mekanis tersebut, peningkatan produktivitas mencapai 6.8% per batch produksi. Selain itu dengan alat tersebut waktu pemisahan ekstrak menjadi 20 menit lebih cepat dibanding dengan pemisahan secara manual. Dengan adanya alat tersebut proses pengambilan ekstrak menjadi efisien dan optimal sehingga dapat meningkatkan produktivitas yang akan berpengaruh pada peningkatan kesejahteraan pemilik dan karyawan, serta memperluas lapangan pekerjaan dan memperluas pemasaran. Kata Kunci: Produktivita, Cincau, Pemera