Mycobacteriophage Alexphander Gene <i>94</i> Encodes an Essential dsDNA-Binding Protein during Lytic Infection

Mycobacteriophages are viruses that specifically infect bacterial species within the genera Mycobacterium and Mycolicibacterium. Over 2400 mycobacteriophages have been isolated on the host Mycolicibacterium smegmatis and sequenced. This wealth of genomic data indicates that mycobacteriophage genomes are diverse, mosaic, and contain numerous (35–60%) genes for which there is no predicted function based on sequence similarity to characterized orthologs, many of which are essential to lytic growth. To fully understand the molecular aspects of mycobacteriophage–host interactions, it is paramount to investigate the function of these genes and gene products. Here we show that the temperate mycobacteriophage, Alexphander, makes stable lysogens with a frequency of 2.8%. Alexphander gene 94 is essential for lytic infection and encodes a protein predicted to contain a C-terminal MerR family helix–turn–helix DNA-binding motif (HTH) and an N-terminal DinB/YfiT motif, a putative metal-binding motif found in stress-inducible gene products. Full-length and C-terminal gp94 constructs form high-order nucleoprotein complexes on 100–500 base pair double-stranded DNA fragments and full-length phage genomic DNA with little sequence discrimination for the DNA fragments tested. Maximum gene 94 mRNA levels are observed late in the lytic growth cycle, and gene 94 is transcribed in a message with neighboring genes 92 through 96. We hypothesize that gp94 is an essential DNA-binding protein for Alexphander during lytic growth. We proposed that gp94 forms multiprotein complexes on DNA through cooperative interactions involving its HTH DNA-binding motif at sites throughout the phage chromosome, facilitating essential DNA transactions required for lytic propagation

The entorhinal cortex of Megachiroptera: a comparative study of Wahlberg's epauletted fruit bat and the straw-coloured fruit bat

This study describes the organisation of the entorhinal cortex of the Megachiroptera, Strawcoloured fruit bat and Wahlberg’s epauletted fruit bat. Using Nissl and Timm stains, parvalbumin and SMI-32 immunohistochemistry, we identified 5 fields within the medial(MEA) and lateral (LEA) entorhinal areas. MEA fields ECL and EC are characterised by a poor differentiation between layers II and III, a distinct layer IV and broad, stratified layers V and VI. LEA fields EI, ER and EL are distinguished by cell clusters in layer II, a clear differentiation between layers II and III, a wide columnar layer III, and a broad sublayer Va. Clustering in LEA layer II was more typical of the Straw-coloured fruit bat. Timm-staining was most intense in layers Ib and II across all fields, and layer III of field ER. Parvalbuminlike staining varied along a medio-lateral gradient with highest immunoreactivity in layers II and III of MEA and more lateral fields of LEA. Sparse SMI-32-like immunoreactivity was seen only in Wahlberg’s epauletted fruit bat. Of the neurons in MEA layer II, ovoid stellate cells account for ~38%, polygonal stellate cells for ~8%, pyramidal cells for ~18%, oblique pyramidal cells for ~6%, and other neurons of variable morphology for ~29%. Differences between bats and other species in cellular make-up and cytoarchitecture of layer II may relate to their 3-dimensional habitat. Cytoarchitecture of layer V in conjunction with high encephalisation and structural changes in the hippocampus suggest similarities in efferent hippocampal-entorhinal-cortical interactions between fruit bats and primates

Evaluation and optimization of multiple fluorophore analysis of a Pseudomonas aeruginosa biofilm

Conventional laser scanning microscopy for multiple fluorescent stains can be a useful tool if the problems of autofluorescence and cross-talk are eliminated. The technique of spectral imaging was employed to unmix five different fluorophores – ranging in emission from 435 to 665 nm – applied to a Pseudomonas aeruginosa biofilm with overlapping spectra and which was not possible using traditional channel mode operation. Using lambda scanning and linear unmixing, the five fluorophores could be distinguished with regions of differentiation apparent