Magazine R877 of the photosynthates is transferred from Ostreobium to the coral, extending the time it can survive without zooxanthellae. So, what's the verdict, good or bad?Boring algae clearly have important functions in reef ecosystems and will influence how they cope with climate change and ocean acidification in the near future. However, we cannot yet give a verdict as to whether they will act as a buffer against these environmental changes or make the situation worse. Little is known about the ecophysiological diversity of boring algae, hence their response is difficult to predict. Recent research shows that the genotypic diversity of Ostreobium is remarkably rich, leading us to speculate that this will be reflected in their physiological diversity and geographical distributions. While this will complicate the interpretation of research outcomes not taking this diversity into account, it also opens up an exciting avenue of research into the details of the functional multiplicity of boring algae.Where can I find out more?

Summary Copper (Cu) is an essential metal that is toxic at high concentrations. Thus, pathogens often rely on host Cu for growth, but host cells can hyper-accumulate Cu to exert anti-microbial effects. The human fungal pathogen Cryptococcus neoformans encodes various Cu-responsive genes but their role in infection is unclear. We determine that pulmonary C. neoformans infection results in Cu-specific induction of genes encoding the Cu-detoxifying metallothionein (Cmt) proteins. Mutant strains lacking CMTs or expressing Cmt variants defective in Cu-coordination exhibit severely attenuated virulence and reduced pulmonary colonization. Consistent with the up-regulation of Cmt proteins, C. neoformans pulmonary infection results in increased serum Cu concentrations and respectively increases and decreases alveolar macrophage expression of the Cu importer, Ctr1, and ATP7A, a transporter implicated in phagosomal Cu compartmentalization. These studies indicate that the host mobilizes Cu as an innate anti-fungal defense but that C. neoformans senses and neutralizes toxic Cu to promote infection.

Summary In this work we describe the identification of a copper‐inducible regulon in Mycobacterium tuberculosis (Mtb). Among the regulated genes was Rv0190/MT0200, a paralogue of the copper metalloregulatory repressor CsoR. The five‐locus regulon, which includes a gene that encodes the copper‐protective metallothionein MymT, was highly induced in wild‐type Mtb treated with copper, and highly expressed in an Rv0190/MT0200 mutant. Importantly, the Rv0190/MT0200 mutant was hyper‐resistant to copper. The promoters of all five loci share a palindromic motif that was recognized by the gene product of Rv0190/MT0200. For this reason we named Rv0190/MT0200 RicR for regulated in copper repressor. Intriguingly, several of the RicR‐regulated genes, including MymT, are unique to pathogenic Mycobacteria. The identification of a copper‐responsive regulon specific to virulent mycobacterial species suggests copper homeostasis must be maintained during an infection. Alternatively, copper may provide a cue for the expression of genes unrelated to metal homeostasis, but nonetheless necessary for survival in a host.

The putative proteasome‐associated proteins Mpa (Mycobaterium proteasomal ATPase) and PafA (proteasome accessory factor A) of the human pathogen Mycobacterium tuberculosis (Mtb) are essential for virulence and resistance to nitric oxide. However, a direct link between the proteasome protease and Mpa or PafA has never been demonstrated. Furthermore, protein degradation by bacterial proteasomes in vitro has not been accomplished, possibly due to the failure to find natural degradation substrates or other necessary proteasome co‐factors. In this work, we identify the first bacterial proteasome substrates, malonyl Co‐A acyl carrier protein transacylase and ketopantoate hydroxymethyltransferase, enzymes that are required for the biosynthesis of fatty acids and polyketides that are essential for the pathogenesis of Mtb. Maintenance of the physiological levels of these enzymes required Mpa and PafA in addition to proteasome protease activity. Mpa levels were also regulated in a proteasome‐dependent manner. Finally, we found that a conserved tyrosine of Mpa was essential for function. Thus, these results suggest that Mpa, PafA, and the Mtb proteasome degrade bacterial proteins that are important for virulence in mice.

Prokaryotic ubiquitin-like protein (Pup) in Mycobacterium tuberculosis (Mtb) is the first known post-translational small protein modifier in prokaryotes, and targets several proteins for degradation by a bacterial proteasome in a manner akin to ubiquitin (Ub) mediated proteolysis in eukaryotes. To determine the extent of pupylation in Mtb, we used tandem affinity purification to identify its “pupylome”. Mass spectrometry identified 55 out of 604 purified proteins with confirmed pupylation sites. Forty-four proteins, including those with and without identified pupylation sites, were tested as substrates of proteolysis in Mtb. Under steady state conditions, the majority of the test proteins did not accumulate in degradation mutants, suggesting not all targets of pupylation are necessarily substrates of the proteasome under steady state conditions. Four proteins implicated in Mtb pathogenesis, Icl (isocitrate lyase), Ino1 (inositol-1-phosphate synthase), MtrA (Mtb response regulator A) and PhoP (phosphate response regulator P), showed altered levels in degradation defective Mtb. Icl, Ino1 and MtrA accumulated in Mtb degradation mutants, suggesting these proteins are targeted to the proteasome. Unexpectedly, PhoP was present in wild type Mtb but undetectable in the degradation mutants. Taken together, these data demonstrate that pupylation regulates numerous proteins in Mtb and may not always lead to degradation.