Small Things Considered

Minicells on Target

The gold ring everyone in cancer chemotherapy is reaching for is the ability to selectively kill cancer cells without damaging normal ones.  Easier said than done.  So far, clever attempts at delivering potent drugs straight to the cancer cells using techniques such as conjugating them to antibodies specific to those cells, have been inconclusive at best.  Now, a group of Australian investigators report promising results using bacterial minicells as the drug delivery system.  (This research is highlighted in Nature Review: Drug Discovery.)

Talmudic Question #20

If viruses did not exist, could anyone have conjured them up?

Bacteria and the Single Auklet

Crested Auklets.
Source: US Geological
Survey.

Crested Auklets are arctic seabirds that use smell for social functions. This wouldn't exactly be news for any other group of animals, but it is a first for birds─those feathered creatures which can both smell and be smelly. These particular monogamous birds have a species-specific tangerine-like odor that attracts their mates. The question arises, where do the chemicals responsible for this scent (mainly cis-4-decenal and octanal) come from?

Comments on Bacterial Mitosis: What's Taking So Long?

This mini-essay garnered some particularly insightful and provocative comments. We think they deserve their own posting. We hope the discussion continues.

Samantha Orchard

I think it is interesting that while quite a bit is now known about the segregation of some bacterial plasmids (as described in this blog entry), relatively little is known about bacterial chromosome segregation. I wonder if it isn't a combination of the small size of the bacteria (as noted above) and the fact that any proteins required for chromosome segregation are essential for cell viability and are therefore less easily studied? Also, it should be noted that a few labs have proposed that bacterial chromosome segregation might occur without the need for specific segregation proteins.

Microblogology

Last May, a group of microbiologically-oriented bloggers were interviewed by Chris Condayan of the American Society for Microbiology's MicrobeWorld. This video ("Microblogology") features John Logsdon, Jonathan Badger, Yersinia, Larry Moran, Tara Smith, and myself. We talk about why we blog, what we think is the role of blogging in science, and our views of the greatest microbiological discoveries in the past decade.

Pseudomonas aeruginosa: Versatile Pathogen and Drug Addict?

Pseudomonas aeruginosa is the most versatile of all known pathogens. Few if any bacteria can match its metabolic versatility and the breadth of its host range─from plants to humans. This species is a paradigm of an opportunistic pathogen of humans, being nearly ubiquitous in our habitats but not usually causing disease in healthy people. There is, however, a unique aspect to its taste as a pathogen:  it is something of a specialist. It occupies center stage in infections of people with certain predisposing conditions, e.g., cystic fibrosis, burns, abrasions of the cornea, and neutropenia (the decrease in the number of neutrophils).

While it is a frequent invader of various organs and tissues, it is not on the top of the list of agents that infect severely immunodeficient persons, such as AIDS patients. So what accounts for this organism's idiosyncratic preference for certain conditions?

Talmudic Question #19

You are stranded on a desert island. During a walk on the beach, you stub your toe against a bottle, which rolls against a rock and breaks. A genie is liberated, eager to grant you one wish. You ask for a microbiological laboratory fully equipped to your specifications. The genie grants you that but with the condition that you can study only one sample. What sample would you collect for study, what would you do with it, and why?

An Update on Mitochondria and Their Invaders

There is more to the bacterial invasion of mitochondria than we had known. Previously, we divulged that bacteria can be found within the mitochondria of certain Italian cockroaches, an unusual form of parasitism if there ever was one. Erin Banning of the Marine Biological Laboratory at Woods Hole told us of a paper that points out similarities between this invasion and that of Bdellovibrio. In both cases the predator grows in the periplasm of the host "cell"─an unusual place for a parasite to grow. The title of the paper tells all: "A symbiont of the tick Ixodes ricinus invades and consumes mitochondria in a mode similar to that of the parasitic bacterium Bdellovibrio bacteriovorus." We already wondered if the Bdellovibrio-type mechanism is limited to bacterial predation of bacteria. Sure, mitochondria were once bacteria, but... 

Thanks, Erin.

Tetracycline: Assassin, Aphrodisiac, Agent Provocateur, Choreographer

by Merry

Bacteroides fragilis.
(c) Source Molecular Corporation
www.sourcemolecular.com

When first used clinically, tetracycline was effective against members of the genus Bacteroides, gram-negative anaerobes that make up 20-30% of our colonic bacterial population. Though usually well-behaved, Bacteroides are opportunistic pathogens capable of causing life-threatening infections if the colon is perforated. Now, virtually all Bacteroides clinical isolates are resistant to tetracycline, and all resistant Bacteroides contain a conjugative transposon (CTn) that carries the resistance gene.

CTns promote mating and their own transfer from host to host, sometimes to a different species or genus, sometimes even crossing the gram negative/gram positive divide.