Marcelo Gonzalez

Sea urchin Arbacia dufresnei (Blainville 1825) larvae response to ocean acidification

Increased atmospheric CO2 emissions are inducing changes in seawater carbon chemistry, lowering its pH, decreasing carbonate ion availability and reducing calcium carbonate saturation state. This phenomenon, known as ocean acidification, is happening at a faster rate in cold regions, i.e., polar and sub-polar waters. The larval development of Arbacia dufresnei from a sub-Antarctic population was studied at high (8.0), medium (7.7) and low (7.4) pH waters. The results show that the offspring from sub-Antarctic populations of A. dufresnei are susceptible to a development delay at low pH, with no significant increase in abnormal forms. Larvae were isometric between pH treatments. Even at calcium carbonate (CaCO3) saturation states (of both calcite and aragonite, used as proxies of the magnesium calcite) <1, skeleton deposition occurred. Polar and sub-polar sea urchin larvae can show a certain degree of resilience to acidification, also emphasizing A. dufresnei potential to poleward migrate and further colonize southern regions.

CLONING AND EXPRESSION ANALYSIS OF ALLOGRAFT INFLAMMATORY FACTOR TYPE 1 IN COELOMOCYTES OF ANTARCTIC SEA URCHIN (STERECHINUS NEUMAYERI)

ABSTRACT We have cloned and characterized for the first time an allograft inflammatory factor 1 (Sn-AIF-1) from the Antarctic sea urchin. We report the cloning of Sn-AIF-1 cDNA and the characterization of its expression in coelomocytes after a bacterial challenge. The cDNA Sn-AIF-1 has a size of 608 bp and encodes a polypeptide of 151 aa. The deduced amino acid sequence has a putative size of 17.430 Da, an isoelectric point of 4.92, and shows 2 elongation factor handlike motifs that normally bind calcium ions. BLAST analysis revealed close matches with other known AIF-1. The deduced amino acid sequence of Sn-AIF-1 showed high homology with AIF-1 in vertebrates such as fish, mice, and humans; and in the case of invertebrates, the major degree of identity (55%) was with a predicted sequence of the purple sea urchin AIF-1, and 52% corresponded to a sponge. Expression of Sn-AIF-1 mRNA was analyzed by qPCR. Sn-AIF-1 mRNA expression was measured from coelomocytes after a bacterial challenge using RT-PCR and revealed that the gene was upregulated after 24 h. Sn-AIF-1 could participate in the inflammatory response, particularly in the activation of coelomocytes and their survival.

Multiple-antibiotic-resistant bacteria from the maritime Antarctic

The existence of multiple-antibiotic-resistant strains of environmental bacteria is commonly linked to human activities. However, multiple-antibiotic-resistant strains of bacteria are also widely found in the Antarctic that has limited human activity. This study was conducted to examine the prevalence of antibiotic-resistant strains among Antarctic bacteria. Forty-five bacterial strains from Estrellas lake of King George Island and Crater lake of Deception Island, Antarctic, were exposed to 30 different antibiotics. Forty out of the 45 bacterial strains were affiliated to 12 genera, Aeromicrobium, Arthrobacter, Bacillus, Brevundimonas, Cryobacterium, Dyadobacter, Flavobacterium, Methylibium, Pedobacter, Pseudomonas, Rhodococcus, and Sphingomonas. Among the bacteria, 43 strains were resistant to at least three antibiotics, and 26 strains were resistant to 10 or more different antibiotics. Pseudomonas spp. and four unknown Microbacteriaceae bacteria were found to be resistant to majority of the antibiotics tested. Two bacteria, each from Estrellas and Crater lakes, were sensitive to all the antibiotics tested. These results indicated that Antarctic bacteria are probably the reservoirs for antibiotic resistance genes.

Characterisation of a cryptic plasmid from an Antarctic bacterium Pedobacter cryoconitis strain BG5.

A cryptic plasmid, pMWHK1 recovered from an Antarctic bacterium Pedobacter cryoconitis BG5 was sequenced and characterised. The plasmid is a circular 6206bp molecule with eight putative open reading frames designated as orf1, orf2, orf3, orf4, orf5, orf6, orf7 and orf8. All the putative open reading frames of pMWHK1 are found to be actively transcribed. Proteins encoded by orf2 and orf4 are predicted to be responsible for the mobilization and replication of the plasmid respectively. orf4 shares 55% and 61% identities with the theta-type Rep proteins from two strains of Riemerella anatipestifer. This suggests that pMWHK1 could be a member of the theta-type replicating plasmid. The origin of replication is located within the AT-rich region upstream of orf4. orf5 and orf6 encode bacterial toxin-antitoxin proteins predicted to maintain plasmid stability. orf3 encodes an entry exclusion protein that is hypothetically involved in reducing the frequency of DNA transfer through conjugation. orf1, orf7 and orf8 encode proteins with unknown functions. Plasmid, pMWHK1 is stably maintained in P. cryoconitis BG5 at 20°C.

Cepa antártica de Bacillus sp., con actividad extracelular de tipo agarolítica y alginatoliasa

Diversas bacterias asociadas a macroalgas pueden usar ficocoloides como fuente de carbono. Las bacterias de la Antartica, poseen caracteristicas fisiologicas adaptativas que habrian evolucionado para permitir su supervivencia y funcionamiento dentro de las condiciones adversas de ese ecosistema. Por lo tanto, bacterias aisladas desde algas antarticas podrian tener la capacidad de degradar enzimaticamente azucares complejos a temperaturas inferiores que aquellas aisladas desde zonas mas calidas, lo que potencialmente podria tener aplicaciones en la mejora en procesos industriales que utilizan enzimas. El analisis del gen ribosomal 16S indica que la cepa bacteriana aislada desde algas varadas en la Isla Rey Jorge (Antartica), pertenece al genero Bacillus. El sobrenadante libre de celulas presento actividad agarasa y alginatoliasa. Se encontraron diferencias significativas en la temperatura optima para hidrolizar agarosa y alginato, evaluada dentro de un rango de 4 a 30 °C. La actividad agarolitica fue mayor a 4 °C, mientras que la actividad alginatoliasa fue mayor a 30 °C. Estos resultados poseen un alto valor biotecnologico y podria ser utilizada con fines industriales.