Biology subjects

McCallum, M.

Publications and source records attributed to McCallum, M..

2 recordsLinked to original sources

bioRxiv2018

Homing and egg discrimination in the Western Slimy Salamander, Plethodon albagula (Caudata: Plethodontidae)

In some species of vertebrates egg brooding is a costly form of parental care. Therefore, misdirection of parental care can significantly lower a females fitness. Because of the maternal investment and increased survivorship to offspring from egg guarding, a brooding female should home to her nest site after being displaced a short distance and discriminate between her own eggs and eggs from other females. In this study, we experimentally tested, in the field, alternative hypotheses concerning homing ability and egg discrimination in a population of nesting western slimy salamanders (Plethodon albagula). Fourteen brooding females were displaced 1 m to the left or right of their nest sites (determined randomly) for the homing experiment. Furthermore, brooding females (n = 13) were presented with their own clutches, which were displaced 50 cm to the left or right (determined randomly), and unfamiliar egg clutches at their original nest sites. The females were released at an equal distance from both egg clutches. After 24 hours, 12 displaced females (86%) had returned to their own nest sites and were brooding their egg clutches. Also, after 24 hours, nine test females had returned to their own nest sites and were brooding the unfamiliar egg clutches. No control or test females were present at the other new nest site locations. Therefore, we suggest that brooding female P. albagula do home to their nest sites and exhibit indirect egg discrimination.

animal behavior and cognition↗

bioRxiv2016

The molecular mechanism of the type IVa pilus motors

Type IVa pili are protein filaments essential for virulence in many bacterial pathogens; they extend and retract from the surface of bacterial cells to pull the bacteria forward with unprecedented force. They are used for attachment, swarming and twitching motility, biofilm formation, up-regulation of other virulence factors, and natural competence. The pilus is assembled by the motor subcomplex which consists of the inner membrane protein PilC and the cytoplasmic ATPase PilB. How PilB catalyzes this process is unknown, due in part to the lack of high-resolution structural information. Phylogenetic analysis of PilB-like ATPases, including GspE, PilT, BfpD, FlaI, and archaeal GspE2 revealed highly conserved residues essential for function in this family of ATPases. Here we report the structure of the core ATPase domains of Geobacter metalloreducens PilB bound to ADP and the non-hydrolysable ATP analogue, AMPPNP, at 3.4 and 2.3[A], respectively. Importantly, these structures were determined in non-saturating nucleotide conditions, revealing important differences in nucleotide binding between chains. Analysis of these differences revealed the sequential turnover of nucleotide by the chains, and the corresponding domain movements. Our data indicate a clockwise rotation of movement in PilB, which would support the assembly of a right-handed helical pilus. Conversely, our analysis suggests a counterclockwise rotation in PilT that would enable right-handed pilus disassembly. The proposed model provides insight into how this family of ATPases can power pilus extension and retraction with extraordinary forces.

microbiology↗