Extracellular heme peroxidases in actinomycetes: a case of mistaken identity

Actinomycetes secrete into their surroundings a suite of enzymes involved in the biodegradation of plant lignocellulose; these have been reported to include both hydrolytic and oxidative enzymes, including peroxidases. Reports of secreted peroxidases have been based upon observations of peroxidase-like activity associated with fractions that exhibit optical spectra reminiscent of heme peroxidases, such as the lignin peroxidases of wood-rotting fungi. Here we show that the appearance of the secreted pseudoperoxidase of the thermophilic actinomycete Thermomonospora fusca BD25 is also associated with the appearance of a heme-like spectrum. The species responsible for this spectrum is a metalloporphyrin; however, we show that this metalloporphyrin is not heme but zinc coproporphyrin. The same porphyrin was found in the growth medium of the actinomycete Streptomyces viridosporus T7A. We therefore propose that earlier reports of heme peroxidases secreted by actinomycetes were due to the incorrect assignment of optical spectra to heme groups rather than to non-iron-containing porphyrins and that lignin-degrading heme peroxidases are not secreted by actinomycetes. The porphyrin, an excretory product, is degraded during peroxidase assays. The low levels of secreted peroxidase activity are associated with a nonheme protein fraction previously shown to contain copper. We suggest that the role of the secreted copper-containing protein may be to bind and detoxify metals that can cause inhibition of heme biosynthesis and thus stimulate porphyrin excretion.     

Theories of cell ageing: a case of mistaken identity

In social insects which reproduce by colony fission there is often only one queen in each swarm (e.g. honeybees, army ants) and the number of males greatly exceeds the number of new queens produced at swarming time. This seems to contradict Fisher's principle that there should be equal investment in male and female reproductives. Hamilton 1975 has suggested that the principle can be saved by counting the investment in the swarm as part of the investment in female reproductives. Craig 1980, on the other hand, argues that few queens are produced because any further investment in queens would be wasted since a queen without a swarm is valueless; on this view the sex ratio is male-biased because of local competition between queens for swarms. The present paper investigates from first principles how many males should be produced by a species which reproduces by colony fission and how the workers should divide themselves between the new colonies. The results of the analysis do not support Hamilton's conjecture but show that a number of factors are involved in the evolution of male production, including kin selection and the relationship between the “fitness” of a colony and the number of workers in it.     

DNA barcoding exposes a case of mistaken identity in the fern horticultural trade

Using cheilanthoid ferns, we provide an example of how DNA barcoding approaches can be useful to the horticultural community for keeping plants in the trade accurately identified. We use plastid rbcL, atpA, and trnG-R sequence data to demonstrate that a fern marketed as Cheilanthes wrightii (endemic to the southwestern USA and northern Mexico) in the horticultural trade is, in fact, Cheilanthes distans (endemic to Australia and adjacent islands). Public and private (accessible with permission) databases contain a wealth of DNA sequence data that are linked to vouchered plant material. These data have uses beyond those for which they were originally generated, and they provide an important resource for fostering collaborations between the academic and horticultural communities. We strongly advocate the barcoding approach as a valuable new technology available to the horticulture industry to help correct plant identification errors in the international trade.     

A case of mistaken identity: accidental ingestion of coins causing esophageal impaction in an elderly female

Coin impaction of the esophagus is infrequently seen in adults, and multiple coin impaction has not been described. The patient was an 85-year-old blind female who presented with 2 days of dysphagia and odynophagia following an attempt to take her medications at bedtime. She reported an esophageal injury from endotracheal intubation during a surgery 6 months earlier. Radiographs showed a radiopaque circular mass in the midesophagus. Endoscopy showed 3 US coins--a nickel, a dime, and a penny--stacked together and impacted on a stricture at 27 cm from the gums. An overtube was planned, but preplacement evaluation showed the lumen was smaller than the coin diameters. An attempt with a retrieval net was unsuccessful. The patient then underwent endotracheal intubation and the coins were removed individually with rat-tooth foreign body forceps. She recovered and underwent successful endoscopic dilation 3 weeks later. She remains asymptomatic since dilation. A brief review of coin impaction and endoscopic management is discussed. Endotracheal intubation for airway protection during endoscopy is recommended for these patients.     

A case of mistaken identity: skin filaments are unreliable for identifying Hippocampus guttulatus and Hippocampus hippocampus

The presence or absence of skin filaments is an unreliable character for identifying European seahorses. Growth of skin filaments on Hippocampus guttulatus coincides with maturation, while presence on Hippocampus hippocampus is highly variable. Multiple morphological traits including snout, head and trunk shape should be used for identification.