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Mitochondria produce energy through oxidative phosphorylation (OXPHOS), which depends on the expression of both nuclear and mitochondrial DNA (mtDNA). In metazoans, a striking exception from strictly maternal inheritance of mitochondria is doubly uniparental inheritance (DUI). This unique system involves the maintenance of two highly divergent mtDNAs (F-and M-type, 8-40% of nucleotide divergence) associated with gametes, and occasionally coexisting in somatic tissues. To address whether metabolic differences underlie this condition, we characterized the OXPHOS activity of oocytes, spermatozoa, and gills of different species through respirometry. DUI species express different gender-linked mitochondrial phenotypes in gametes and partly in somatic tissues. The M-phenotype is specific to sperm and entails (i) low coupled/uncoupled respiration rates, (ii) a limitation by the phosphorylation system, and (iii) a null excess capacity of the final oxidases, supporting a strong control over the upstream complexes. To our knowledge, this is the first example of a phenotype resulting from direct selection on sperm mitochondria. This metabolic remodelling suggests an adaptive value of mtDNA variations and we propose that bearing sex-linked mitochondria could assure the energetic requirements of different gametes, potentially linking male-energetic adaptation, mitotype preservation and inheritance, as well as resistance to both heteroplasmy and ageing.

Little is known about how genetic variation at the nucleotide level contributes to competitive fitness within species. During a 6,000-generation study of Bacillus subtilis evolved under relaxed selection for sporulation, a new strain, designated WN716, emerged with significantly different colony and cell morphologies; loss of sporulation, competence, acetoin production, and motility; multiple auxotrophies; and increased competitive fitness (H. Maughan and W. L. Nicholson, Appl. Environ. Microbiol. 77:4105-4118, 2011). The genome of WN716 was analyzed by OpGen optical mapping, whole-genome 454 pyrosequencing, and the CLC Genomics Workbench. No large chromosomal rearrangements were found; however, 34 single-nucleotide polymorphisms (SNPs) and ؉1 frameshifts were identified in WN716 that resulted in amino acid changes in coding sequences of annotated genes, and 11 SNPs were located in intergenic regions. Several classes of genes were affected, including biosynthetic pathways, sporulation, competence, and DNA repair. In several cases, attempts were made to link observed phenotypes of WN716 with the discovered mutations, with various degrees of success. For example, a ؉1 frameshift was identified at codon 13 of sigW, the product of which (SigW) controls a regulon of genes involved in resistance to bacteriocins and membrane-damaging antibiotics. Consistent with this finding, WN716 exhibited sensitivity to fosfomycin and to a bacteriocin produced by B. subtilis subsp. spizizenii and exhibited downregulation of SigW-dependent genes on a transcriptional microarray, consistent with WN716 carrying a knockout of sigW. The results suggest that propagation of B. subtilis for less than 2,000 generations in a nutrient-rich environment where sporulation is suppressed led to rapid initiation of genomic erosion.The phenotypic plasticity of bacterial genomes enables bacteria to alter their gene expression in response to environmental stresses (18). A well-studied example of one such stress is the transition of Bacillus subtilis cells from exponential growth into the stationary phase upon nutrient limitation (49). Transition state genes in B. subtilis include those involved in such global responses as chemotaxis and motility; production of extracellular enzymes; production of, and resistance to, antibiotics; genetic competence; and initiation of sporulation (reviewed in reference 46). Sporulation itself is a complex developmental process requiring over 125 genes and taking about 6 to 8 h (7,13,48). Of these genes, about 21% are pleiotropic, i.e., also involved in housekeeping and other cellular processes (20). Thus, relaxing selective pressure for sporulation would be predicted to reduce the genetic interference from sporulation in pleiotropic genes and to allow greater potential for their variation in a population (14). Understanding how sporulating bacteria evolve under constant sporulation-repressing conditions can help us further elucidate how genes interact at the whole-organism level.Laboratory evolution experiments have becom...

The effect of biofilm was assayed for Farfantepenaeus brasiliensis postlarvae fed with commercial pellets. Indoor tanks in a zero water exchange system were used, considering: shrimp fed with biofilm and commercial feed (B+F), and shrimp fed only with commercial feed (F); both receiving polyethylene sheets as artificial substrates. For B+F, sheets were placed 15 days before the trial into a heterotrophic medium (containing diatom Thalassiosira weissflogii, commercial feed, molasses and wheat bran in a 20 C:1 N ratio) to promote biofilm development. For F, clean sheets were used and daily replaced to avoid biofilm formation. Biofilm chlorophyll a concentration, micro‐organisms density and water quality were determined weekly. Also, a stomach content analysis was made. An increase in chlorophyll a concentration was observed in biofilm during the experiment, characterized mainly by pennate diatoms, filamentous cyanobacteria, flagellates, ciliates, nematodes and rotifers. Most of these items were found in the stomach of shrimp; however, no significant differences in growth were detected between treatments. Survival was significantly higher and nitrite concentrations were significantly lower when biofilm was present. The results indicate that the use of biofilm could be considered a good tool during F. brasiliensis nursery phase, mainly by improving survival through the maintenance of water quality.

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One of the best known crustacean hormones is the crustacean hyperglycemic hormone (CHH). However, the mechanisms involved in hormone release in these animals are poorly understood, and thus constitute the central objective of the present study. Different groups of crustaceans belonging to diverse taxa (Chasmagnathus granulata, a grapsid crab and Orconectes limosus, an astacid) were injected with serotonin, fluoxetine, or a mixture of both, and glycemic values (C. granulata and O. limosus) and CHH levels (O. limosus) were determined after 2 h in either submerged animals or animals exposed to atmospheric air. Both serotonin and fluoxetine caused significant hyperglycemia (P<0.05) after injection into the blood sinus of the two species, an effect enhanced after exposure to atmospheric air. In C. granulata blood glucose increased from 6.1 to 43.3 and 11.4 mg/100 ml in submerged animals and from 5.7 to 55.2 and 22.5 mg/100 ml in air-exposed animals after treatment with serotonin and fluoxetine, respectively. In O. limosus the increases were from 1.2 to 59.7 and 135.2 mg/100 ml in submerged animals and from 2.5 to 200.3 and 193.6 mg/100 ml in air-exposed animals after treatment with serotonin and fluoxetine, respectively. Serotonin and fluoxetine also caused a significant increase in the circulating levels of CHH in O. limosus, from 11.9 to 43 and 45.7 fmol/ml in submerged animals and from 13.2 to 32.6 and 45.7 fmol/ml in air-exposed animals, respectively, thus confirming their action as neuroregulators in these invertebrates.