Flavonoids are nearly ubiquitous in plants and are recognized as the pigments responsible for the colors of leaves, especially in autumn. They are rich in seeds, citrus fruits, olive oil, tea, and red wine. They are low molecular weight compounds composed of a three-ring structure with various substitutions. This basic structure is shared by tocopherols (vitamin E). Flavonoids can be subdivided according to the presence of an oxy group at position 4, a double bond between carbon atoms 2 and 3, or a hydroxyl group in position 3 of the C (middle) ring. These characteristics appear to also be required for best activity, especially antioxidant and antiproliferative, in the systems studied. The particular hydroxylation pattern of the B ring of the flavonoles increases their activities, especially in inhibition of mast cell secretion. Certain plants and spices containing flavonoids have been used for thousands of years in traditional Eastern medicine. In spite of the voluminous literature available, however, Western medicine has not yet used flavonoids therapeutically, even though their safety record is exceptional. Suggestions are made where such possibilities may be worth pursuing.

The Effects of Plant Flavonoids on Mammalian Cells:Implications for Inflammation, Heart Disease, and Cancer

Occurrence, metabolism, metabolic role, and industrial uses of bacterial polyhydroxyalkanoates.

The BLOLOG redox technology based on tetrazolium dye reduction as an indicator of sole-carbon-source utilization was evaluated as a rapid, community-level method to characterize and classify heterotrophic microbial communities. Direct incubation of whole environmental samples (aquatic, soil, and rhizosphere) in BIOLOG plates containing 95 separate carbon sources produced community-dependent patterns of sole-carbon-source utilization. Principal-component analysis of color responses quantified from digitized images of plates revealed distinctive patterns among microbial habitats and spatial gradients within soil and estuarine sites. Correlation of the original carbon source variables to the principal components gives a functional basis to distinctions among communities. Intensive spatial and temporal analysis of microbial communities with this technique can produce ecologically relevant classifications of heterotrophic microbial communities.

Classification and characterization of heterotrophic microbial communities on the basis of patterns of community-level sole-carbon-source utilization.

Communities of microscopic plant life, or phytoplankton, dominate the Earth's aquatic ecosystems. This important new book by Colin Reynolds covers the adaptations, physiology and population dynamics of phytoplankton communities in lakes and rivers and oceans. It provides basic information on composition, morphology and physiology of the main phyletic groups represented in marine and freshwater systems and in addition reviews recent advances in community ecology, developing an appreciation of assembly processes, co-existence and competition, disturbance and diversity. Although focussed on one group of organisms, the book develops many concepts relevant to ecology in the broadest sense, and as such will appeal to graduate students and researchers in ecology, limnology and oceanography.

/pdf/the-ecology-of-phytoplankton-4ev70n3jsq.pdf

The Ecology of Phytoplankton

Occurrence, classification, and biological function of hydrogenases: an overview.

In nature, bacteria alternate between two modes of growth: a unicellular life phase, in which the cells are free-swimming (planktonic), and a multicellular life phase, in which the cells are sessile and live in a biofilm, that can be defined as surface-associated microbial heterogeneous structures comprising different populations of microorganisms surrounded by a self-produced matrix that allows their attachment to inert or organic surfaces. While a unicellular life phase allows for bacterial dispersion and the colonization of new environments, biofilms allow sessile cells to live in a coordinated, more permanent manner that favors their proliferation. In this alternating cycle, bacteria accomplish two physiological transitions via differential gene expression: (i) from planktonic cells to sessile cells within a biofilm, and (ii) from sessile to detached, newly planktonic cells. Many of the innate characteristics of biofilm bacteria are of biotechnological interest, such as the synthesis of valuable compounds (e.g., surfactants, ethanol) and the enhancement/processing of certain foods (e.g., table olives). Understanding the ecology of biofilm formation will allow the design of systems that will facilitate making products of interest and improve their yields.

/pdf/living-together-in-biofilms-the-microbial-cell-factory-and-1hxchub20f.pdf

Living together in biofilms: the microbial cell factory and its biotechnological implications.

The anaerobic zones of Lakes Cis6 and Vilar (Banyoles karstic area, NE Spain) had mass developments of purple sulfur bacteria during summer 1982. In Lake Vilar, Chromatium spp. was dominant (up to 92% of the microbial biovolume). In Lake Ciso, the predominant microorganisms were Chromatium spp. (up to 7 1%) and another purple sulfur bacterium forming aggregates (20%). The bacterial layer could be divided according to the physiological state of the cells into a top part of maximal specific activity, a peak of maximal abundance, and a bottom part of inactive cells. The bacteria in the peak were predominantly limited by light; sulfide, phosphate, and acetate were not limiting in the middle of the day. The light limitation started at the depth having the maximal concentration of cells; the top of the layer appeared to be sulfide-limited. Specific contents of photopigments, elemental sulfur, and reserve polymers decreased from the top to the bottom of the bacterial layer. These phenomena point to the crucial role of light in the development of layers of phototrophic bacteria in stratified lakes.

https://aslopubs.onlinelibrary.wiley.com/doi/pdf/10.4319/lo.1985.30.5.0919

Phototrophic sulfur bacteria in two Spanish lakes: Vertical distribution and limiting factors1

We present a testable model for the origin of the nucleus, the membrane-bounded organelle that defines eukaryotes. A chimeric cell evolved via symbiogenesis by syntrophic merger between an archaebacterium and a eubacterium. The archaebacterium, a thermoacidophil resembling extant Thermoplasma, generated hydrogen sulfide to protect the eubacterium, a heterotrophic swimmer comparable to Spirochaeta or Hollandina that oxidized sulfide to sulfur. Selection pressure for speed swimming and oxygen avoidance led to an ancient analogue of the extant cosmopolitan bacterial consortium "Thiodendron latens." By eubacterial-archaebacterial genetic integration, the chimera, an amitochondriate heterotroph, evolved. This "earliest branching protist" that formed by permanent DNA recombination generated the nucleus as a component of the karyomastigont, an intracellular complex that assured genetic continuity of the former symbionts. The karyomastigont organellar system, common in extant amitochondriate protists as well as in presumed mitochondriate ancestors, minimally consists of a single nucleus, a single kinetosome and their protein connector. As predecessor of standard mitosis, the karyomastigont preceded free (unattached) nuclei. The nucleus evolved in karyomastigont ancestors by detachment at least five times (archamoebae, calonymphids, chlorophyte green algae, ciliates, foraminifera). This specific model of syntrophic chimeric fusion can be proved by sequence comparison of functional domains of motility proteins isolated from candidate taxa.

https://www.pnas.org/content/pnas/97/13/6954.full.pdf

The chimeric eukaryote: Origin of the nucleus from the karyomastigont in amitochondriate protists

Symbiogenesis is the result of the permanent coexistence of various bionts to form the holobiont (namely, the host and its microbiota). The holobiome is the sum total of the component genomes in a eukaryotic organism; it comprises the genome of an individual member of a given taxon (the host genome) and the microbiome (the genomes of the symbiotic microbiota). The latter is made up of the genes of a variety of microbial communities that persist over time and are not eliminated by natural selection. Therefore, the holobiome can also be considered as the genomic reflection of the complex network of symbiotic interactions that link an individual member of a given taxon with its associated microbiome. Eukaryotic individuals can be analyzed as coevolved, tightly integrated, prokaryotic communities; in this view, natural selection acts on the holobiont as if it were an integrated unit. The best studied holobionts are those that emerged from symbioses involving insects. The presence of symbiotic associations throughout most of the evolutionary history of insects suggests that they were a driving force in the diversification of this group. Support for the evolutionary importance of symbiogenesis comes from the observation that the gradual passage from an ancestral to a descendant species by the accumulation of random mutations has not been demonstrated in the field, nor in the laboratory, nor in the fossil record. Instead, symbiogenesis expands the view of the point-mutationonly as the unique mechanisms of evolution and offers an explanation for the discontinuities in the fossil record (“punctuated equilibrium”). As such, it challenges conventional paradigms in biology. This review describes the relationships between xylophagous insects and their microbiota in an attempt to understand the characteristics that have determined bacterial fidelity over generations and throughout evolutionary history. [ Int Microbiol 2013; 16(3):133-143] Keywords: symbiogenesis · symbiosis · holobiont · holobiome · microbiota · microbiome · coevolution

Symbiogenesis: the holobiont as a unit of evolution.

We develop a symbiogenetic concept of the origin of eukaryotic intracellular motility systems from anaerobic but aerotolerant spirochetes in sulfide-rich environments. The last eukaryotic common ancestors (LECAs) have extant archaeprotist descendants: motile nucleated cells with Embden-Meyerhof glycolysis and substrate-level phosphorylation that lack the α-proteobacterial symbiont that became the mitochondrion. Swimming and regulated O2-tolerance via sulfide oxidation already had been acquired by sulfidogenic wall-less archaebacteria (thermoplasmas) after aerotolerant cytoplasmic-tubule-containing spirochetes (eubacteria) attached to them. Increasing stability of sulfide-oxidizing/sulfur-reducing consortia analogous to extant sulfur syntrophies (Thiodendron) led to fusion. The eubacteria–archaebacteria symbiosis became permanent as the nucleus evolved by prokaryotic recombination with membrane hypertrophy, analogous to Gemmata obscuriglobus and other δ-proteobacteria with membrane-bounded nucleoids. Histone-coated DNA, protein-synthetic RNAs, amino-acylating, and other enzymes were contributed by the sulfidogen whereas most intracellular motility derives from the spirochete. From this redox syntrophy in anoxic and microoxic Proterozoic habitats LECA evolved. The nucleus originated by recombination of eu- and archaebacterial DNA that remained attached to eubacterial motility structures and became the microtubular cytoskeleton, including the mitotic apparatus. Direct LECA descendants include free-living archaeprotists in anoxic environments: archamoebae, metamonads, parabasalids, and some mammalian symbionts with mitosomes. LECA later acquired the fully aerobic Krebs cycle-oxidative phosphorylation-mitochondrial metabolism by integration of the protomitochondrion, a third α-proteobacterial symbiont from which the ancestors to most protoctists, all fungi, plants, and animals evolved. Secondarily anaerobic eukaryotes descended from LECA after integration of this oxygen-respiring eubacterium. Explanatory power and experimental predictions for molecular biology of the LECA concept are stated.

https://www.pnas.org/content/pnas/103/35/13080.full.pdf

Ricardo Guerrero

Papers

Living together in biofilms: the microbial cell factory and its biotechnological implications.

Phototrophic sulfur bacteria in two Spanish lakes: Vertical distribution and limiting factors1

The chimeric eukaryote: Origin of the nucleus from the karyomastigont in amitochondriate protists

Symbiogenesis: the holobiont as a unit of evolution.

The last eukaryotic common ancestor (LECA): Acquisition of cytoskeletal motility from aerotolerant spirochetes in the Proterozoic Eon