Bioactive molecules from Nocardia: diversity,bioactivities and biosynthesis

Journal of Industrial Microbiology & Biotechnology - Nocardia spp. are catalase positive, aerobic, and non-motile Gram-positive filamentous bacteria. Many Nocarida spp. have been reported as...     

Initial impacts and field validation of host range for Boreioglycaspis melaleucae Moore (Hemiptera: Psyllidae), a biological control agent of the invasive tree Melaleuca quinquenervia (Cav.) Blake (Myrtales: Myrtaceae: Leptospermoideae)

Invasion of south Florida wetlands by the Australian paperbark tree, Melaleuca quinquenervia (Cav.) S.T. Blake (melaleuca), has caused adverse economic and environmental impacts. The tree's biological attributes and favorable ambient biophysical conditions combine to complicate efforts to restore and maintain south Florida ecosystems. Management requires an integrated strategy that deploys multiple biological control agents to forestall reinvasion and to supplement other control methods, thereby lessening recruitment and regeneration after removal of existing trees. This biological control program began during 1997 when an Australian weevil, Oxyops vitiosa (Pascoe), was released. A second Australian insect, the melaleuca psyllid (Boreioglycaspis melaleucae Moore), first introduced during 2002, has also widely established. After inoculation of the psyllid in a field study, only 40% of seedlings survived herbivory treatments compared with 95% survival in controls. The resultant defoliation also reduced growth of the surviving seedlings. A weevil-induced decline at a site comprised mainly of coppicing stumps had slowed after a 70% reduction. Psyllids colonized the site, and 37% of the remaining coppices succumbed within 10 mo. The realized ecological host range of B. melaleucae was restricted to M. quinquenervia; 18 other nontarget plant species predicted to be suboptimal or nonhosts during laboratory host range testing were unaffected when interspersed with psyllid-infested melaleuca trees in a common garden study. Evaluations are ongoing, but B. melaleucae is clearly reducing seedling recruitment and stump regrowth without adversely impacting other plant species. Manifestation of impacts on mature trees will require more time, but initial indications suggest that the psyllid will be an effective supplement to the weevil.     

New moves in motor control

Motor behaviour results from information processing across multiple neural networks acting at all levels from initial selection of the behaviour to its final generation. Understanding how motor behaviour is produced requires identifying the constituent neurons of these networks, their cellular properties, and their pattern of synaptic connectivity. Neural networks have been traditionally studied with neurophysiological and neuroanatomical approaches. These approaches have been highly successful in particularly suitable 'model' preparations, typically ones in which the numbers of neurons in the networks were relatively small, neural network composition was unvarying across individual animals, and the preparations continued to produce fictive motor patterns in?vitro. However, analysing networks without these characteristics, and analysing the complete ensemble of networks that cooperatively generate behaviours, is difficult with these approaches. Recently developed molecular and neurogenetic tools provide additional avenues for analysing motor networks by allowing individual or groups of neurons within networks to be manipulated in novel ways and allowing experiments to be performed not only in?vitro but also in?vivo. We review here some of the new insights into motor network function that these advances have provided and indicate how these advances might bridge gaps in our understanding of motor control. To these ends, we first review motor neural network organisation highlighting cross-phylum principles. We then use prominent examples from the field to show how neurogenetic approaches can complement classical physiological studies, and identify additional areas where these approaches could be advantageously applied.     

Non-surgical Intratracheal Instillation of Mice with Analysis of Lungs and Lung Draining Lymph Nodes by Flow Cytometry

Phagocytic cells such as alveolar macrophages and lung dendritic cells (LDCs) continuously sample antigens from the alveolar spaces in the lungs. LDCs, in particular, are known to migrate to the lung draining lymph nodes (LDLNs) where they present inhaled antigens to T cells initiating an appropriate immune response to a variety of immunogens^1,2. To model interactions between the lungs and airborne antigens in mice, antigens can be administered intranasally^1,3,4, intratracheally⁵ or as aerosols⁶. Delivery by each route involves distinct technical skills and limitations that need to be considered before designing an experiment. For example, intranasal and aerosolized exposure delivers antigens to both the lungs and the upper respiratory tract. Hence antigens can access the nasal associated lymphoid tissue (NALT)⁷, potentially complicating interpretation of the results. In addition, swallowing, sneezing and the breathing rate of the mouse may also lead to inconsistencies in the doses delivered. Although the involvement of the upper respiratory tract may be preferred for some studies, it can complicate experiments focusing on events specifically initiated in the lungs. In this setting, the intratracheal (i.t) route is preferable as it delivers test materials directly into the lungs and bypasses the NALT. Many i.t injection protocols involve either blind intubation of the trachea through the oral cavity or surgical exposure of the trachea to access the lungs. Herein, we describe a simple, consistent, non-surgical method for i.t instillation. The opening of the trachea is visualized using a laryngoscope and a bent gavage needle is then inserted directly into the trachea to deliver the innoculum. We also describe procedures for harvesting and processing of LDLNs and lungs for analysis of antigen trafficking by flow cytometry.Download video file.^{(48M, mov)}     

Biological control of <Emphasis Type="Italic">Melaleuca quinquenervia</Emphasis>: an Everglades invader

A massive effort is underway to restore the Florida Everglades, mainly by re-engineering hydrology to supply more water to the system at appropriate times of the year. However, correcting water flow patterns alone will not restore the associated plant communities due to habitat-transforming effects of invasive species, in particular the Australian wetland tree Melaleuca quinquenervia (Cav.) S. T. Blake (Myrtales, Myrtaceae), which has invaded vast areas and transformed sawgrass marshes into dense, biologically impoverished, structurally altered forest habitats. To address this threat, an invasive species reduction program was launched that combined mechanical removal and herbicidal control to remove mature trees with the release of specialized insects to suppress seed production and lower seedling survival. Melaleuca has now been removed from most public lands while biological control has limited its ability to regenerate and reinvade from nearby infestations often located on unmanaged privately held lands. This case illustrates how restoration of highly modified ecosystems may require both restoration of physical conditions (water flow), and suppression of high impact or transformative invaders, showing well the need to integrate biological control into conservation biology.     

Post-biological control invasion trajectory for Melaleuca quinquenervia in a seasonally inundated wetland

The recruitment and mortality of Melaleuca quinquenervia seedlings were evaluated over a 3-year period in a seasonally inundated wetland in the western Everglades region. The mean (±SE) density of seedlings/saplings m^?1 declined from 64.8 (±4.5) to 0.5 (±0.2) over the 3 years, a population reduction of 99.2%. Four distinct water regimes characterized this site: dry, dry to wet transition, flooded, and wet to dry transition. Seedling recruitment was highest in the dry to wet transition and lowest in the flooded water regime, while mortality was highest under flooded and dry water regimes. The mean estimate of population growth (λ) across water regimes was 0.64 ± 0.05 indicating negative population growth. Elimination of introduced insect herbivores using insecticides did not reduce mortality of recruited M. quinquenervia seedlings/saplings indicating that direct herbivory was not responsible for the decline in seedling density. On the other hand, a mean of only 0.2 (±0.03) viable seeds m^?2 d^?1 fell into the plots, an amount considerably lower than in previous studies. We submit that change in the invasion trajectory M. quinquenervia was most likely caused by reduced seed inputs from aerial seed banks depleted by insect herbivory rather than direct herbivory on seedlings. This may indicate a fundamental alteration of M. quinquenervia population dynamics ultimately resulting in a less invasive and, therefore, less ecologically damaging species.     

Can genomics clarify the origins of Boreioglycaspis melaleucae in California,USA?

The Australian psyllid Boreioglycaspis melaleucae is a biological control agent of Melaleuca quinquenervia in Florida (USA) but was observed attacking M. quinquenervia trees in southern California (USA). Genotyping revealed the California population matched three of eight Australian haplotypes and all three Florida haplotypes. It remains unclear if the California psyllid population arrived directly from Australia or via Florida.     

Sensory pathways and their modulation in the control of locomotion

Recent experiments have extended our understanding of how sensory information in premotor networks controlling motor output is processed during locomotion, and at what level the efficacy of specific sensory—motor pathways is determined. Phasic presynaptic inhibition of sensory transmission combined with postsynaptic alterations of excitatory and inhibitory synaptic transmission from interneurons of the premotor networks contribute to the modulation of reflex pathways and to the generation of reflex reversal. These mechanisms play an important role in adapting the operation of central networks to external demands and thus help optimize sensory—motor integration.     

Monosynaptic connections mediate resistance reflex in crayfish (Procambarus clarkii) walking legs

Summary In crustacean walking legs, the coxo-basipodite chordotonal organ (CB) composed of about 50 sensory cells, evokes a resistance reflex in the levator (Lev) and depressor (Dep) muscles responsible for the movements of the coxo-basipodite joint where it is located. Mechanical stimulation of the CB strand and electrical stimulation of its sensory nerve have been performed along with systematic intracellular recordings from CB terminals (CB T) and levator (Lev) or depressor (Dep) motoneurons (MNs) in order to study their connections. Measurements of conduction times in the CB nerve demonstrated different pools of sensory fibres, the fastest of which reach the ganglion in 2.5 ms. During imposed movements to the CB strand, intracellularly recorded Lev or Dep MN display EPSPs that are correlated to spikes in the CB nerve, their delays are incompatible with a polysynaptic pathway. Systematic stimulation of the CB nerve demonstrates that about 4 to 8 CB fibres are connected with each Lev or Dep MN. Classical tests for monosynaptic connections indicate that EPSPs occurring between 3 ms and 6 ms correspond mainly to monosynaptic connections with CB T, whereas IPSPs (the latencies of which are above 12 ms) are polysynaptic. In spite of the high selectivity of the CB T onto MNs, eight simultaneous intracellular recordings of coupled CB T and MN (out of more than 300 MNs penetrated) have allowed a direct measurement of synaptic delays (less than 1 ms). The functional significance of these results is discussed in relation to the proprioceptive control of locomotor movements.Abbreviations CB Coxo-basipodite chordotonal organ - CB n CB sensory nerve - CB T CB sensory terminal - Dep depressor - Lev levator - MN motoneuron