Pioneer settlement of the cold-water coral Desmophyllum dianthus (Esper, 1794) on plastic

Larval settlement is a critical step for sessile benthic species such as corals, whose ability to thrive on diverse natural and anthropogenic substrates may lead to a competitive advantage in the colonization of new environments with respect to a narrow tolerance for a specific kind of substratum. Plastic debris, widespread in marine waters, provides a large, motile, and solid substratum supporting a highly diverse biological community. Here we present the first observation of a floating plastic bottle colonized by the deep-sea coral Desmophyllum dianthus. The density pattern and co-occurring species composition suggest a pioneer behavior of this coral species, whose peculiar morphologic plasticity response when interacting with the plastic substrate (i.e., low density polyethylene) has not been observed before. The tolerance of D. dianthus for such plastic substrate may affect ecological processes in deep water environments, disrupting interspecific substrate competition in the benthic community.

A molecular rack and pinion actuates a cell-surface adhesin and enables bacterial gliding motility

The gliding bacterium Flavobacterium johnsoniae is known to have an adhesin, SprB, that moves along the cell surface on a spiral track. Following viscous shear, cells can be tethered by the addition of an anti-SprB antibody, causing spinning at 3 Hz. Labeling the type 9 secretion system (T9SS) with a YFP fusion of GldL showed a yellow fluorescent spot near the rotation axis, indicating that the motor driving the motion is associated with the T9SS. The distance between the rotation axis and the track (90 nm) was determined after adding a Cy3 label for SprB. A rotary motor spinning a pinion of radius 90 nm at 3 Hz would cause a spot on its periphery to move at 1.5 μm/s, the gliding speed. We suggest the pinion drives a flexible tread that carries SprB along a track fixed to the cell surface. Cells glide when this adhesin adheres to the solid substratum.

A molecular rack and pinion actuates a cell-surface adhesin and enables bacterial gliding motility

The mechanism for bacterial gliding is not understood. The gliding bacteriumFlavobacterium johnsoniaeis known to have an adhesin, SprB, that moves along the cell surface on a spiral track. When cells are sheared by passage of a suspension through thin tubing, they stop gliding but can be tethered by addition of an anti-SprB antibody. Tethered cells spin about 3 Hz. We labeled the Type 9 secretion system (T9SS) with a yellow-fluorescent-protein (YFP) fusion of GldL. When labeled cells were tethered, a yellow fluorescent spot was found near the rotation axis, which shows that the motor that drives the rotation localizes with the T9SS. The spiral track was labeled by following the motion of Cy3 attached to SprB via an antibody. The distance between the rotation axis and the track was determined by a measurement involving both labels, YFP and Cy3, yielding 90 nm. If a rotary motor spins a pinion of radius 90 nm 3 Hz, a spot on its periphery will move 1.5 μm/s, the speed at which cells glide. We suggest that the pinion drives a flexible tread that carries SprB along a track fixed to the cell surface. Cells glide when such an adhesin adheres to the solid substratum.

Effectiveness of different methods of preparing seedlings of cereals under sterile conditions for investigations of nucleic acids using radioactive precursors

On seedlings grown from grain not sterilized in advance bacteria numbered more than 10⁸ microorganisms per one gram of fresh weight. Washing of seedlings with cetyltrimethylammonium bromide or sodium lauryl sulphate solutions reduced the number of bacteria several times. Sterilization of grains prior to planting with sodium hypochlorite and germination on solid substratum (perlit) reduced the number of bacteria to below 10⁴ microorganisms to one gram of fresh weight. If germination was, however, in water, bacteria on the seedlings were approximately as numerous as on seedlings from mon-sterilized grains. Of the three antibiotics tested (streptomycin, chloramphenicol, penicillin) the most effective against the bacteria of wheat seedlings was chloramphenicol coupled with streptomycin; of antibiotics used singly chloramphenicol was best.

State-building and the Management of Diversity in India (Thirteenth to Seventeenth Centuries)

How has political diversity—and, first of all, administrative and institutional diversity—been handled within the succeeding polities that prevailed in the Indian subcontinent from 1200 to 1700? In order to provide the non-specialist reader with a first insight into this complex question, the present article opens with a presentation of the sources available for reconstructing the administrative organisation and functioning of medieval and early modern Indian polities. Despite the fragmentary and biased nature of the information they provide, these sources (mainly epigraphic materials and narrative texts) have often been elevated to the rank of a solid substratum that allowed for the development of highly sophisticated yet antagonistic analyses of both the nature and the working of the Indian state in pre-British times. Besides a strong focus on the question of centralisation, most of these analyses have also long been marred by an implicit but ever-present Western point of comparison. From the middle of the 1980s, however, a number of voices have argued in favour of an alternative approach that would value both the processual character of state- and institution-building and its ideological dimension while stressing at the same time the need to take into account the diversity of the forms assumed by this process in the various regions that came to constitute a given polity and to pay more attention to the wide range of actors involved in state-formation and to the latter’s political cultures. Taking its cue from these non-aligned or revisionist studies, as they are often termed, the last part of the essay shifts from the purely institutional perspective presiding over the first and largely historiographical section and proposes to examine instead the politics of diversity that were theorised and implemented by pre-colonial South Asian dynasties as well as the way these politics were perceived and handled by those who bore their brunt most directly, that is to say the subordinate functional elites.

Biofilm Susceptibility to Antimicrobials

Microbial biofilms, where organisms are intimately associated with each other and a solid substratum through binding and inclusion within an exopolymer matrix, are widely distributed in nature and disease. In the mouth, multispecies biofilms are associated not only with dental plaque and tooth decay but also with soft tissues of the buccal cavity and with most forms of periodontal disease. Organization of micro-organisms within biofilms confers, on the component species, properties which are not evident with the individual species grown independently or as planktonic populations in liquid media. While many of these properties relate to the establishment of functional, mixed-species consortia within the exopolymeric matrices, others relate to the establishment of physico-chemical gradients, within the biofilm, that modify the metabolism of the component cells. A consequence of biofilm growth that has profound implications for their control in the environment and in medicine is a markedly enhanced resistance to chemical antimicrobial agents and antibiotics. Mechanisms associated with such resistance in biofilms will form the substance of the present review. While some aspects of biofilm resistance are yet only poorly understood, the dominant mechanisms are thought to be related to: (i) modified nutrient environments and suppression of growth rate within the biofilm; (ii) direct interactions between the exopolymer matrices, and their constituents, and antimicrobials, affecting diffusion and availability; and (iii) the development of biofilm/attachmentspecific phenotypes.