Trabecular architecture and joint loading of the proximal humerus in extant hominoids,Ateles, and Australopithecus africanus

Objectives

Several studies have investigated potential functional signals in the trabecular structure of the primate proximal humerus but with varied success. Here, we apply for the first time a “whole‐epiphyses” approach to analysing trabecular bone in the humeral head with the aim of providing a more holistic interpretation of trabecular variation in relation to habitual locomotor or manipulative behaviors in several extant primates and Australopithecus africanus.

Materials and methods

We use a “whole‐epiphysis” methodology in comparison to the traditional volume of interest (VOI) approach to investigate variation in trabecular structure and joint loading in the proximal humerus of extant hominoids, Ateles and A. africanus (StW 328).

Results

There are important differences in the quantification of trabecular parameters using a “whole‐epiphysis” versus a VOI‐based approach. Variation in trabecular structure across knuckle‐walking African apes, suspensory taxa, and modern humans was generally consistent with predictions of load magnitude and inferred joint posture during habitual behaviors. Higher relative trabecular bone volume and more isotropic trabeculae in StW 328 suggest A. africanus may have still used its forelimbs for arboreal locomotion.

Discussion

A whole‐epiphysis approach to analysing trabecular structure of the proximal humerus can help distinguish functional signals of joint loading across extant primates and can provide novel insight into habitual behaviors of fossil hominins.

     

Cyanobacterial formation of intracellular Ca‐carbonates in undersaturated solutions

Cyanobacteria have long been thought to induce the formation of Ca‐carbonates as secondary by‐products of their metabolic activity, by shifting the chemical composition of their extracellular environment to conditions favoring mineral precipitation. Some cyanobacterial species forming Ca‐carbonates intracellularly were recently discovered. However, the environmental conditions under which this intracellular biomineralization process can occur and the impact of cyanobacterial species forming Ca‐carbonates intracellularly on extracellular carbonatogenesis are not known. Here, we show that these cyanobacteria can form Ca‐carbonates intracellularly while growing in extracellular solutions undersaturated with respect to all Ca‐carbonate phases, that is, conditions thermodynamically unfavorable to mineral precipitation. This shows that intracellular Ca‐carbonate biomineralization is an active process; that is, it costs energy provided by the cells. The cost of energy may be due to the active accumulation of Ca intracellularly. Moreover, unlike cyanobacterial strains that have been usually considered before by studies on Ca‐carbonate biomineralization, cyanobacteria forming intracellular carbonates may slow down or hamper extracellular carbonatogenesis, by decreasing the saturation index of their extracellular solution following the buffering of the concentration of extracellular calcium to low levels.     

Using antagonistic soil bacteria and their cell‐free filtrates to control the black rot pathogen Xanthomonas campestris pv. campestris

Xanthomonas campestris pv. campestris (Xcc) is a phytopathogenic bacteria, and it is the causative agent of black rot in crucifers. Recent studies have shown that Bacillus species have strong biological control on Xanthomonas. One of the mechanisms of this control is secondary metabolites production. A collection of 257 bacteria isolated from a suppressive soil was evaluated for in vitro antagonistic activity against X. campestris, and 92 isolates (44.6%) were able to inhibit its growth. Among the 92 isolates evaluated in the double‐layer technique, 51 (55.43%) inhibited Xcc growth on the inhibition tests with cell‐free filtrates (CFF) in liquid medium. Thirteen of these isolates presented 50% or more growth inhibition, and five isolates presented 100% growth inhibition of Xcc. The CFF of the isolate TCDT‐08, which belongs to the Paenibacillus genus, was used for in vivo tests with kale crops. The artificial inoculation of kale with Xcc‐629IBSBF pretreated with CFF from the isolate TCDT‐08 demonstrated that the bacterium loses the ability of colonizing kale and of causing black rot. A Paenibacillus sp. isolate has strong inhibitory activity against X. campestris pv. campestris, and further studies can result in the use of this isolate to protect kale from Xcc infection.     

Evaluating the role of morphological characters in the phylogeny of some trypanosomatid genera (Excavata,Kinetoplastea, Trypanosomatida)

Over the last three decades, it has been progressively assumed that morphology has become obsolete for trypanosomatid systematics. Traditional taxonomy, based on the occurrence of specific kinds of cell morphotypes during life cycles and the morphometry of such cells, is often rejected by molecular phylogenies inferred mostly from 18S rDNA alone or combined with GAPDH. In such context, we hypothesized the affinities of 35 representatives of seven trypanosomatid genera from separated and combined cladistics analyses of morphological and 18S matrices. Morphology is shown to be more consistent and to have stronger synapomorphy retention than the 18S data. The strict consensus of cladograms from separated analyses was mostly unresolved, while combined analysis produced a meaningful and robust phylogenetic pattern, as evidenced by partition congruence index, Bremer support and frequencies of groups present/contradicted. The results (1) corroborate the separation of Angomonas and Strigomonas from Crithidia, which is now shown to be monophyletic, (2) support the revalidation of the genus Wallaceina, and (3) place the genera Herpetomonas, Leptomonas and Phytomonas within a single clade. Overall, we demonstrate the belief that morphological characters are inferior to molecular ones for trypanosomatid systematics is a consequence of neglecting their inclusion in phylogenetic analyses.