This results in a fluid outer membrane loosely associated with the cell wall. In addition, Leptospira have a flagellum located in the periplasm, associated with corkscrew style movement. Chemoreceptors at the poles of the bacteria sense various substrates and change the direction of its movement. The bacteria are traditionally visualised using dark-field microscopy without staining.A total of 66 species of Leptospira has been identified. Based on their genomic sequence, they are divided into two clades and four subclades: P1, P2, S1, and S2. The 19 members of the P1 subclade include the 8 species that can cause severe disease in humans: L. alexanderi, L. borgpetersenii, L. interrogans, L. kirschneri, L. mayottensis, L. noguchii, L. santarosai, and L. weilii. The P2 clade comprises 21 species that may cause mild disease in humans. The remaining 26 species comprise the S1 and S2 subclades, which include "saprophytes" known to consume decaying matter (saprotrophic nutrition). Pathogenic Leptospira do not multiply in the environment. Leptospira require high humidity for survival but can remain alive in environments such as stagnant water or contaminated soil. The bacterium can be killed by temperatures of 50 °C (122 °F) and can be inactivated by 70% ethanol, 1% sodium hypochlorite, formaldehyde, detergents and acids.Leptospira are also classified based on their serovar. The diverse sugar composition of the lipopolysaccharide on the surface of the bacteria is responsible for the antigenic difference between serovars. About 300 pathogenic serovars of Leptospira are recognised.
(2008)
A research group led by Namnyak has found that although there is a lot of media coverage of Stockholm syndrome, there has not been a lot of research into the phenomenon. What little research has been done is often contradictory and does not always agree on what Stockholm syndrome is. The term has grown beyond kidnappings to all definitions of abuse. It stated that there is no clear definition of symptoms to diagnose the syndrome. FBI law enforcement bulletin (1999)
A 1998 report by the FBI containing over 1,200 hostage incidents found that only 8% of kidnapping victims showed signs of Stockholm syndrome. When victims who showed negative and positive feelings toward the law enforcement personnel are excluded, the percentage decreases to 5%. A survey of 600 police agencies in 1989, performed by the FBI and the University of Vermont, found not a single case when emotional involvement between the victim and the kidnapper interfered with or jeopardized an assault. In short, this database provides empirical support that the Stockholm syndrome remains a rare occurrence. The sensational nature of dramatic cases causes the public to perceive this phenomenon as the rule rather than the exception. The bulletin concludes that, although depicted in fiction and film and often referred to by the news media, the phenomenon actually occurs rarely. Therefore, crisis negotiators should place the Stockholm syndrome in proper perspective.