Production of vitamin B12 in an upflow anaerobic filter continuous reactor using Acetobacterium sp.

The accumulation of biofilm by Acetobacterium sp. during continuous culture in an upflow anaerobic filter (UAF) growing on methanol-formate was the result of space velocity and inlet concentrations of substrate and Co⁺². To achieve good development of biofilm, a space velocity of 0.38 h^–1, inlet substrate concentrations of 125 mM of both methanol and formate, and Co⁺² at 0.16 mM were required. Cell productivities in the effluent of the UAF-reactor were about 6-fold higher than in chemostat cultures (0.20 g l^–1 h^–1 for UAF and 0.035 g l^–1 h^–1 for chemostat) (previous studies), and the maximum vitamin B₁₂ specific concentration was 5.1 mg g cell^–1.     

How tetrapods feed in water: a functional analysis by paradigm

Mechanical theory is used to erect a paradigm predicting the manipulations used by carnivorous aquatic amphibians, reptiles, birds and mammals to catch, subdue, process and swallow their prey. These predictions are confirmed by observational evidence. Most aquatic predatory tetrapods use long, prehensile tooth-armed jaws as pincer jaws to snap shut onto the prey and catch and kill it, although some use the flexibility of long necks in spear fishing and some odontocetes may stun prey with sonar. Most do not have cutting or nipping dentitions as these cannot be used on prey which is freely floating. They use caniniform dentition to hold and kill prey, or in some cases crushing dentition to break open hard-shelled prey. They dismember prey by dynamic loading, snatching bites so quickly that the prey tears. They use shake feeding, shaking the prey apart from side to side above the water. If the prey is too large to lift above the water they use twist feeding, twisting pieces off. Small pieces are easily swallowed but larger pieces are held above the water and swallowed by tilting the head back in gravity feeding, or by jerking the head back and forth in incrtial feeding. Some animals use mobile jaws to pull prey back into the mouth in ratchet feeding. Filter feeding evades these problems by feeding on very small prey. The use of paradigms in functional analysis is discussed with special reference to this work. The paradigm method is shown to be the most suitable one. There has been repeated convergent and parallel evolution of adaptations to feed in water.     

Methanotrophs of the Psychrophilic Microbial Community of the Russian Arctic Tundra

In tundra, at a low temperature, there exists a slowly developing methanotrophic community. Methane-oxidizing bacteria are associated with plants growing at high humidity, such as sedge and sphagnum; no methanotrophs were found in polytrichous and aulacomnious mosses and lichens, typical of more arid areas. The methanotrophic bacterial community inhabits definite soil horizons, from moss dust to peat formed from it. The potential ability of the methanotrophic community to oxidize methane at 5°C enhances with the depth of the soil profile in spite of the decreasing soil temperature. The methanotrophic community was found to gradually adapt to various temperatures due to the presence of different methane-oxidizing bacteria in its composition. Depending on the temperature and pH, different methanotrophs occupy different econiches. Within a temperature range from 5 to 15°C, three morphologically distinct groups of methanotrophs could be distinguished. At pH 5–7 and 5–15°C, forms morphologically similar to Methylobacter psychrophilus predominated, whereas at the acidic pH 4–6 and 10–15°C, bipolar cells typical of Methylocella palustris were mostly found. The third group of methanotrophic bacteria growing at pH 5–7 and 5–10°C was represented by a novel methanotroph whose large coccoid cells had a thick mucous capsule.     

Streamlined Purification of Plasmid DNA From Prokaryotic Cultures

We describe the complete process of AcroPrep Advance Filter Plates for 96 plasmid preparations, starting from prokaryotic culture and ending with high purity DNA. Based on multi-well filtration for bacterial lysate clearance and DNA purification, this method creates a streamlined process for plasmid preparation. Filter plates containing silica-based media can easily be processed by vacuum filtration or centrifuge to yield appreciable quantities of plasmid DNA. Quantitative analyses determine the purified plasmid DNA is consistently of high quality with average OD_260/280 ratios of 1.97. Overall, plasmid yields offer more pure DNA for downstream applications, such as sequencing and cloning. This streamlined method of using AcroPrep Advance Filter Plates allows for manual, semi-automated or fully-automated processing.     

Morphological specialization of heterantherous Rhynchanthera grandiflora (Melastomataceae) accommodates pollinator diversity

• The tropical Melastomataceae are characterized by poricidal anthers which constitute a floral filter selecting for buzz‐pollinating bees. Stamens are often dimorphic, sometimes with discernible feeding and pollinating functions. Rhynchanthera grandiflora produces nectarless flowers with four short stamens and one long stamen; all anthers feature a narrow elongation with an upwards facing pore.
• We tested pollen transfer by diverse foraging bees and viability of pollen from both stamen types. The impact of anther morphology on pollen release direction and scattering angle was studied to determine the plant's reproductive strategy.
• Medium‐sized to large bees sonicated flowers in a specific position, and the probability of pollen transfer correlated with bee size even among these legitimate visitors. Small bees acted as pollen thieves or robbers. Anther rostrum and pore morphology serve to direct and focus the pollen jet released by floral sonication towards the pollinator's body. Resulting from the ventral and dorsal positioning of the short and long stamens, respectively, the pollinator's body was widely covered with pollen. This improves the plant's chances of outcrossing, irrespective of which bee body part contacts the stigma. Consequently, R. grandiflora is also able to employ bee species of various sizes as pollen vectors.
• The strategy of spreading pollen all over the pollinator's body is rather cost‐intensive but counterbalanced by ensuring that most of the released pollen is in fact transferred to the bee. Thus, flowers of R. grandiflora illustrate how specialized morphology may serve to improve pollination by a functional group of pollinators.

     

The Mu Transpososome Through a Topological Lens

ABSTRACT

Phage Mu is the most efficient transposable element known, its high efficiency being conferred by an enhancer DNA element. Transposition is the end result of a series of well choreographed steps that juxtapose the enhancer and the two Mu ends within a nucleoprotein complex called the ‘transpososome.’ The particular arrangement of DNA and protein components lends extraordinary stability to the transpososome and regulates the frequency, precision, directionality, and mechanism of transposition. The structure of the transpososome, therefore, holds the key to understanding all of these attributes, and ultimately to explaining the runaway genetic success of transposable elements throughout the biological world. This review focuses on the path of the DNA within the Mu transpososome, as uncovered by recent topological analyses. It discusses why Mu topology cannot be analyzed by standard methods, and how knowledge of the geometry of site alignment during Flp and Cre site-specific recombination was harnessed to design a new methodology called ‘difference topology.’ This methodology has also revealed the order and dynamics of association of the three interacting DNA sites, as well as the role of the enhancer in assembly of the Mu transpososome.