Day: October 15, 2011

Saturday, 15 October 2011

11:43 – This guy makes a pretty good argument on why he expects Greece to default on 28 October. Of course, the Greek government hasn’t yet gotten its grubby little hands on the final bailout payment, so that may give them pause. But it’s not like the EU/ECB/IMF are actually handing over suitcases full of euros, so the reality is that the Greek government really doesn’t get its hands on bailout payments anyway.

As things stand, the Greek government has no intention of ever repaying any of the money it owes other than in the sense of paying back a little bit to get a lot more. And everyone else is fully aware of this. If the EU/ECB/IMF actually does pay the last tranche, it’s only to prop up Greece for a few weeks longer, buying time for them to do what they can to prevent the inevitable Greek default from starting the row of dominoes falling. At this point, that’s pretty much a foregone conclusion, with Portugal and Ireland toppling soon after Greece, followed soon after by Spain, Italy, Belgium, France, and, eventually, Germany itself. I just hope the UK, US, Canada, and other first-world economies can minimize the damage to themselves.

In writing our books, we try very hard to keep the costs of doing home science as low as possible. That means using cheap or free items as much as possible, rather than requiring purchased items. But I’m going to make an exception for the series of lab sessions I’m working on now, which are on culturing bacteria. I’ve done these labs in the past. I used environmental bacteria, but then I’m not an inexperienced high-school student. The risks of culturing environment bacteria, particularly at room temperature, are pretty minimal, but not non-existent. A dropped Petri dish, for example, could put large numbers of pathogenic bacteria into the air.

So I decided to specify a purchased culture of bacteria intended for use by students. There are still minor risks involved, but they’re much smaller than those of culturing unknown bacteria. I’m going to specify a mixed broth culture from Carolina Biological Supply. It’s $17 plus shipping, but it contains three types of bacteria that are useful for learning purposes, and it’d be pretty hard to get into trouble with them.

The three bacteria are Bacillus subtilis (Gram+ rod), Micrococcus luteus (Gram+ sphere), and Rhodospirillum rubrum (Gram- spiral), which gives us all three bacterial shapes and both Gram types. They’re also large enough to be visible without an oil-immersion objective, and they form colonies that are easy to discriminate visually from each other. Finally, they’re reasonably robust, pretty easy to culture on standard nutrient agar or in nutrient broth, and grow reasonably well at room temperature.

We’ll use these bacteria over the course of several sessions. We’ll do a standard agar plate culture to grow and identify colonies of each of the three species. We’ll isolate each of the three and grow pure cultures in broth. We’ll then reculture on agar to grow bacterial “lawns” of each of the pure cultures. Finally, we’ll test the susceptibility of each species to various antibiotics. We may also re-culture resistant bacteria repeatedly to produce a resistant strain.

We don’t want anyone to have to re-purchase the mixed culture because the first one died off, so we’ll probably also experiment with re-culturing in refrigerated nutrient broth and/or phosphate-buffered saline to maintain a live culture over the course of several weeks. I haven’t done this with these species, so I’ll order one of these mixed culture tubes from Carolina to run that part of the procedure myself.

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